[RFC PATCH] fs/lock: increase the filp's reference for Posix-style locks

[RFC PATCH] fs/lock: increase the filp's reference for Posix-style locks

[xiubli]

From: Xiubo Li <xiubli@redhat.com>

When closing the file descripters in parallel in multiple threads,
who are sharing the same file descripters, the filp_close() will
remove all the Posix-style locks. But if two threads both calling
the filp_close() it may race and cause use-after-free crash:

 PID: 327771   TASK: ffff952aa1db3180  CPU: 8    COMMAND: "db2fmp"
  #0 [ffff95202f33b960] machine_kexec at ffffffff890662f4
  #1 [ffff95202f33b9c0] __crash_kexec at ffffffff89122b82
  #2 [ffff95202f33ba90] crash_kexec at ffffffff89122c70
  #3 [ffff95202f33baa8] oops_end at ffffffff89791798
  #4 [ffff95202f33bad0] no_context at ffffffff89075d14
  #5 [ffff95202f33bb20] __bad_area_nosemaphore at ffffffff89075fe2
  #6 [ffff95202f33bb70] bad_area_nosemaphore at ffffffff89076104
  #7 [ffff95202f33bb80] __do_page_fault at ffffffff89794750
  #8 [ffff95202f33bbf0] do_page_fault at ffffffff89794975
  #9 [ffff95202f33bc20] page_fault at ffffffff89790778
     [exception RIP: ceph_fl_release_lock+20]
     RIP: ffffffffc08247a4  RSP: ffff95202f33bcd0  RFLAGS: 00010286
     RAX: ffff952d4ebd8a00  RBX: 0000000000000000  RCX: dead000000000200
     RDX: ffff95202f33bd60  RSI: ffff95202f33bd60  RDI: ffff9526b6ac5b00
     RBP: ffff95202f33bce0   R8: ffff9526b6ac5b18   R9: ffffffffc083c368
     R10: 0000000000001109  R11: 0000000000000000  R12: ffff95202f33bd60
     R13: ffff9526b6ac5b00  R14: 0000000000000000  R15: 0000000000000000
     ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
 #10 [ffff95202f33bce8] locks_release_private at ffffffff892ab3d7
 #11 [ffff95202f33bd00] locks_free_lock at ffffffff892ac34d
 #12 [ffff95202f33bd18] locks_dispose_list at ffffffff892ac44b
 #13 [ffff95202f33bd40] __posix_lock_file at ffffffff892acdfa
 #14 [ffff95202f33bda8] posix_lock_file at ffffffff892ad146
 #15 [ffff95202f33bdb8] ceph_lock at ffffffffc0824e8a [ceph]
 #16 [ffff95202f33bdf8] vfs_lock_file at ffffffff892ad185
 #17 [ffff95202f33be08] locks_remove_posix at ffffffff892ad239
 #18 [ffff95202f33bee0] locks_remove_posix at ffffffff892ad2a0
 #19 [ffff95202f33bef0] filp_close at ffffffff8924baa6
 #20 [ffff95202f33bf18] __close_fd at ffffffff8926f89c
 #21 [ffff95202f33bf40] sys_close at ffffffff8924d503
 #22 [ffff95202f33bf50] system_call_fastpath at ffffffff89799f92
     RIP: 00007f806ec446ab  RSP: 00007f80517f0d90  RFLAGS: 00010206
     RAX: 0000000000000003  RBX: 00007f8030001a20  RCX: 00007f80300386b0
     RDX: 00007f806ef0d880  RSI: 0000000000000001  RDI: 0000000000000006
     RBP: 00007f806ef0e3c0   R8: 00007f80517fa700   R9: 0000000000000000
     R10: 0000000000000000  R11: 0000000000000206  R12: 0000000000000000
     R13: 00007f80300035b0  R14: 00007f80517f1104  R15: 000000000000006c
     ORIG_RAX: 0000000000000003  CS: 0033  SS: 002b

We need to make sure that the filp in the file_lock shouldn't be
release when any file_lock is still referring to it.

For the Posix-style locks, whose owner will be the thread ids, we
will increase the filp's reference.

URL: https://tracker.ceph.com/issues/57986
Signed-off-by: Xiubo Li <xiubli@redhat.com>
---
 drivers/android/binder.c |  2 +-
 fs/file.c                | 15 ++++++++++-----
 fs/locks.c               | 18 +++++++++++++++---
 include/linux/fs.h       | 14 ++++++++++++++
 io_uring/openclose.c     |  3 ++-
 5 files changed, 42 insertions(+), 10 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 880224ec6abb..03692564d940 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -1924,7 +1924,7 @@ static void binder_deferred_fd_close(int fd)
 	if (twcb->file) {
 		// pin it until binder_do_fd_close(); see comments there
 		get_file(twcb->file);
-		filp_close(twcb->file, current->files);
+		filp_close(twcb->file, file_lock_make_thread_owner(current->files));
 		task_work_add(current, &twcb->twork, TWA_RESUME);
 	} else {
 		kfree(twcb);
diff --git a/fs/file.c b/fs/file.c
index 5f9c802a5d8d..39ad8e74a8d9 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -417,6 +417,7 @@ static struct fdtable *close_files(struct files_struct * files)
 	 * files structure.
 	 */
 	struct fdtable *fdt = rcu_dereference_raw(files->fdt);
+	fl_owner_t owner = file_lock_make_thread_owner(files);
 	unsigned int i, j = 0;
 
 	for (;;) {
@@ -429,7 +430,7 @@ static struct fdtable *close_files(struct files_struct * files)
 			if (set & 1) {
 				struct file * file = xchg(&fdt->fd[i], NULL);
 				if (file) {
-					filp_close(file, files);
+					filp_close(file, owner);
 					cond_resched();
 				}
 			}
@@ -653,6 +654,7 @@ static struct file *pick_file(struct files_struct *files, unsigned fd)
 int close_fd(unsigned fd)
 {
 	struct files_struct *files = current->files;
+	fl_owner_t owner = file_lock_make_thread_owner(files);
 	struct file *file;
 
 	spin_lock(&files->file_lock);
@@ -661,7 +663,7 @@ int close_fd(unsigned fd)
 	if (!file)
 		return -EBADF;
 
-	return filp_close(file, files);
+	return filp_close(file, owner);
 }
 EXPORT_SYMBOL(close_fd); /* for ksys_close() */
 
@@ -695,6 +697,7 @@ static inline void __range_cloexec(struct files_struct *cur_fds,
 static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
 				 unsigned int max_fd)
 {
+	fl_owner_t owner = file_lock_make_thread_owner(cur_fds);
 	unsigned n;
 
 	rcu_read_lock();
@@ -711,7 +714,7 @@ static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
 
 		if (file) {
 			/* found a valid file to close */
-			filp_close(file, cur_fds);
+			filp_close(file, owner);
 			cond_resched();
 		}
 	}
@@ -816,6 +819,7 @@ struct file *close_fd_get_file(unsigned int fd)
 
 void do_close_on_exec(struct files_struct *files)
 {
+	fl_owner_t owner = file_lock_make_thread_owner(files);
 	unsigned i;
 	struct fdtable *fdt;
 
@@ -841,7 +845,7 @@ void do_close_on_exec(struct files_struct *files)
 			rcu_assign_pointer(fdt->fd[fd], NULL);
 			__put_unused_fd(files, fd);
 			spin_unlock(&files->file_lock);
-			filp_close(file, files);
+			filp_close(file, owner);
 			cond_resched();
 			spin_lock(&files->file_lock);
 		}
@@ -1080,6 +1084,7 @@ static int do_dup2(struct files_struct *files,
 	struct file *file, unsigned fd, unsigned flags)
 __releases(&files->file_lock)
 {
+	fl_owner_t owner = file_lock_make_thread_owner(files);
 	struct file *tofree;
 	struct fdtable *fdt;
 
@@ -1111,7 +1116,7 @@ __releases(&files->file_lock)
 	spin_unlock(&files->file_lock);
 
 	if (tofree)
-		filp_close(tofree, files);
+		filp_close(tofree, owner);
 
 	return fd;
 
diff --git a/fs/locks.c b/fs/locks.c
index 607f94a0e789..e8b67f87e0ee 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -331,6 +331,8 @@ EXPORT_SYMBOL_GPL(locks_owner_has_blockers);
 /* Free a lock which is not in use. */
 void locks_free_lock(struct file_lock *fl)
 {
+	if (fl->fl_file && file_lock_is_thread_owner(fl->fl_owner))
+		fput(fl->fl_file);
 	locks_release_private(fl);
 	kmem_cache_free(filelock_cache, fl);
 }
@@ -384,7 +386,10 @@ void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
 
 	locks_copy_conflock(new, fl);
 
-	new->fl_file = fl->fl_file;
+	if (file_lock_is_thread_owner(new->fl_owner))
+		new->fl_file = get_file(fl->fl_file);
+	else
+		new->fl_file = fl->fl_file;
 	new->fl_ops = fl->fl_ops;
 
 	if (fl->fl_ops) {
@@ -488,13 +493,14 @@ static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
 	} else
 		fl->fl_end = OFFSET_MAX;
 
-	fl->fl_owner = current->files;
+	fl->fl_owner = file_lock_make_thread_owner(current->files);
 	fl->fl_pid = current->tgid;
-	fl->fl_file = filp;
+	fl->fl_file = get_file(filp);
 	fl->fl_flags = FL_POSIX;
 	fl->fl_ops = NULL;
 	fl->fl_lmops = NULL;
 
+
 	return assign_type(fl, l->l_type);
 }
 
@@ -2243,6 +2249,7 @@ int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock *flock)
 
 		fl->fl_flags |= FL_OFDLCK;
 		fl->fl_owner = filp;
+		fput(filp);
 	}
 
 	error = vfs_test_lock(filp, fl);
@@ -2376,6 +2383,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
 		cmd = F_SETLK;
 		file_lock->fl_flags |= FL_OFDLCK;
 		file_lock->fl_owner = filp;
+		fput(filp);
 		break;
 	case F_OFD_SETLKW:
 		error = -EINVAL;
@@ -2385,6 +2393,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
 		cmd = F_SETLKW;
 		file_lock->fl_flags |= FL_OFDLCK;
 		file_lock->fl_owner = filp;
+		fput(filp);
 		fallthrough;
 	case F_SETLKW:
 		file_lock->fl_flags |= FL_SLEEP;
@@ -2450,6 +2459,7 @@ int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 *flock)
 		cmd = F_GETLK64;
 		fl->fl_flags |= FL_OFDLCK;
 		fl->fl_owner = filp;
+		fput(filp);
 	}
 
 	error = vfs_test_lock(filp, fl);
@@ -2499,6 +2509,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
 		cmd = F_SETLK64;
 		file_lock->fl_flags |= FL_OFDLCK;
 		file_lock->fl_owner = filp;
+		fput(filp);
 		break;
 	case F_OFD_SETLKW:
 		error = -EINVAL;
@@ -2508,6 +2519,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
 		cmd = F_SETLKW64;
 		file_lock->fl_flags |= FL_OFDLCK;
 		file_lock->fl_owner = filp;
+		fput(filp);
 		fallthrough;
 	case F_SETLKW64:
 		file_lock->fl_flags |= FL_SLEEP;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e654435f1651..d7d81962a863 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1028,6 +1028,20 @@ static inline struct file *get_file(struct file *f)
 /* legacy typedef, should eventually be removed */
 typedef void *fl_owner_t;
 
+/*
+ * Set the last significant bit to 1 to mark that
+ * we have get a reference of the fl->fl_file.
+ */
+static inline fl_owner_t file_lock_make_thread_owner(fl_owner_t owner)
+{
+	return (fl_owner_t)((unsigned long)owner | 1UL);
+}
+
+static inline bool file_lock_is_thread_owner(fl_owner_t owner)
+{
+	return ((unsigned long)owner & 1UL);
+}
+
 struct file_lock;
 
 struct file_lock_operations {
diff --git a/io_uring/openclose.c b/io_uring/openclose.c
index 67178e4bb282..5a12cdf7f8d0 100644
--- a/io_uring/openclose.c
+++ b/io_uring/openclose.c
@@ -212,6 +212,7 @@ int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 int io_close(struct io_kiocb *req, unsigned int issue_flags)
 {
 	struct files_struct *files = current->files;
+	fl_owner_t owner = file_lock_make_thread_owner(files);
 	struct io_close *close = io_kiocb_to_cmd(req, struct io_close);
 	struct fdtable *fdt;
 	struct file *file;
@@ -247,7 +248,7 @@ int io_close(struct io_kiocb *req, unsigned int issue_flags)
 		goto err;
 
 	/* No ->flush() or already async, safely close from here */
-	ret = filp_close(file, current->files);
+	ret = filp_close(file, owner);
 err:
 	if (ret < 0)
 		req_set_fail(req);
-- 
2.31.1

Re: [RFC PATCH] fs/lock: increase the filp's reference for Posix-style locks

[Jeff Layton]

On Mon, 2022-11-07 at 17:52 +0800, xiubli@redhat.com wrote:
> From: Xiubo Li <xiubli@redhat.com>
> 
> When closing the file descripters in parallel in multiple threads,
> who are sharing the same file descripters, the filp_close() will
> remove all the Posix-style locks. But if two threads both calling
> the filp_close() it may race and cause use-after-free crash:
> 
>  PID: 327771   TASK: ffff952aa1db3180  CPU: 8    COMMAND: "db2fmp"
>   #0 [ffff95202f33b960] machine_kexec at ffffffff890662f4
>   #1 [ffff95202f33b9c0] __crash_kexec at ffffffff89122b82
>   #2 [ffff95202f33ba90] crash_kexec at ffffffff89122c70
>   #3 [ffff95202f33baa8] oops_end at ffffffff89791798
>   #4 [ffff95202f33bad0] no_context at ffffffff89075d14
>   #5 [ffff95202f33bb20] __bad_area_nosemaphore at ffffffff89075fe2
>   #6 [ffff95202f33bb70] bad_area_nosemaphore at ffffffff89076104
>   #7 [ffff95202f33bb80] __do_page_fault at ffffffff89794750
>   #8 [ffff95202f33bbf0] do_page_fault at ffffffff89794975
>   #9 [ffff95202f33bc20] page_fault at ffffffff89790778
>      [exception RIP: ceph_fl_release_lock+20]
>      RIP: ffffffffc08247a4  RSP: ffff95202f33bcd0  RFLAGS: 00010286
>      RAX: ffff952d4ebd8a00  RBX: 0000000000000000  RCX: dead000000000200
>      RDX: ffff95202f33bd60  RSI: ffff95202f33bd60  RDI: ffff9526b6ac5b00
>      RBP: ffff95202f33bce0   R8: ffff9526b6ac5b18   R9: ffffffffc083c368
>      R10: 0000000000001109  R11: 0000000000000000  R12: ffff95202f33bd60
>      R13: ffff9526b6ac5b00  R14: 0000000000000000  R15: 0000000000000000
>      ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
>  #10 [ffff95202f33bce8] locks_release_private at ffffffff892ab3d7
>  #11 [ffff95202f33bd00] locks_free_lock at ffffffff892ac34d
>  #12 [ffff95202f33bd18] locks_dispose_list at ffffffff892ac44b
>  #13 [ffff95202f33bd40] __posix_lock_file at ffffffff892acdfa
>  #14 [ffff95202f33bda8] posix_lock_file at ffffffff892ad146
>  #15 [ffff95202f33bdb8] ceph_lock at ffffffffc0824e8a [ceph]
>  #16 [ffff95202f33bdf8] vfs_lock_file at ffffffff892ad185
>  #17 [ffff95202f33be08] locks_remove_posix at ffffffff892ad239
>  #18 [ffff95202f33bee0] locks_remove_posix at ffffffff892ad2a0
>  #19 [ffff95202f33bef0] filp_close at ffffffff8924baa6
>  #20 [ffff95202f33bf18] __close_fd at ffffffff8926f89c
>  #21 [ffff95202f33bf40] sys_close at ffffffff8924d503
>  #22 [ffff95202f33bf50] system_call_fastpath at ffffffff89799f92
>      RIP: 00007f806ec446ab  RSP: 00007f80517f0d90  RFLAGS: 00010206
>      RAX: 0000000000000003  RBX: 00007f8030001a20  RCX: 00007f80300386b0
>      RDX: 00007f806ef0d880  RSI: 0000000000000001  RDI: 0000000000000006
>      RBP: 00007f806ef0e3c0   R8: 00007f80517fa700   R9: 0000000000000000
>      R10: 0000000000000000  R11: 0000000000000206  R12: 0000000000000000
>      R13: 00007f80300035b0  R14: 00007f80517f1104  R15: 000000000000006c
>      ORIG_RAX: 0000000000000003  CS: 0033  SS: 002b
> 
> We need to make sure that the filp in the file_lock shouldn't be
> release when any file_lock is still referring to it.
> 
> For the Posix-style locks, whose owner will be the thread ids, we
> will increase the filp's reference.
> 
> URL: https://tracker.ceph.com/issues/57986
> Signed-off-by: Xiubo Li <xiubli@redhat.com>
> ---
>  drivers/android/binder.c |  2 +-
>  fs/file.c                | 15 ++++++++++-----
>  fs/locks.c               | 18 +++++++++++++++---
>  include/linux/fs.h       | 14 ++++++++++++++
>  io_uring/openclose.c     |  3 ++-
>  5 files changed, 42 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 880224ec6abb..03692564d940 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -1924,7 +1924,7 @@ static void binder_deferred_fd_close(int fd)
>  	if (twcb->file) {
>  		// pin it until binder_do_fd_close(); see comments there
>  		get_file(twcb->file);
> -		filp_close(twcb->file, current->files);
> +		filp_close(twcb->file, file_lock_make_thread_owner(current->files));
>  		task_work_add(current, &twcb->twork, TWA_RESUME);
>  	} else {
>  		kfree(twcb);
> diff --git a/fs/file.c b/fs/file.c
> index 5f9c802a5d8d..39ad8e74a8d9 100644
> --- a/fs/file.c
> +++ b/fs/file.c
> @@ -417,6 +417,7 @@ static struct fdtable *close_files(struct files_struct * files)
>  	 * files structure.
>  	 */
>  	struct fdtable *fdt = rcu_dereference_raw(files->fdt);
> +	fl_owner_t owner = file_lock_make_thread_owner(files);
>  	unsigned int i, j = 0;
>  
>  	for (;;) {
> @@ -429,7 +430,7 @@ static struct fdtable *close_files(struct files_struct * files)
>  			if (set & 1) {
>  				struct file * file = xchg(&fdt->fd[i], NULL);
>  				if (file) {
> -					filp_close(file, files);
> +					filp_close(file, owner);
>  					cond_resched();
>  				}
>  			}
> @@ -653,6 +654,7 @@ static struct file *pick_file(struct files_struct *files, unsigned fd)
>  int close_fd(unsigned fd)
>  {
>  	struct files_struct *files = current->files;
> +	fl_owner_t owner = file_lock_make_thread_owner(files);
>  	struct file *file;
>  
>  	spin_lock(&files->file_lock);
> @@ -661,7 +663,7 @@ int close_fd(unsigned fd)
>  	if (!file)
>  		return -EBADF;
>  
> -	return filp_close(file, files);
> +	return filp_close(file, owner);
>  }
>  EXPORT_SYMBOL(close_fd); /* for ksys_close() */
>  
> @@ -695,6 +697,7 @@ static inline void __range_cloexec(struct files_struct *cur_fds,
>  static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
>  				 unsigned int max_fd)
>  {
> +	fl_owner_t owner = file_lock_make_thread_owner(cur_fds);
>  	unsigned n;
>  
>  	rcu_read_lock();
> @@ -711,7 +714,7 @@ static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
>  
>  		if (file) {
>  			/* found a valid file to close */
> -			filp_close(file, cur_fds);
> +			filp_close(file, owner);
>  			cond_resched();
>  		}
>  	}
> @@ -816,6 +819,7 @@ struct file *close_fd_get_file(unsigned int fd)
>  
>  void do_close_on_exec(struct files_struct *files)
>  {
> +	fl_owner_t owner = file_lock_make_thread_owner(files);
>  	unsigned i;
>  	struct fdtable *fdt;
>  
> @@ -841,7 +845,7 @@ void do_close_on_exec(struct files_struct *files)
>  			rcu_assign_pointer(fdt->fd[fd], NULL);
>  			__put_unused_fd(files, fd);
>  			spin_unlock(&files->file_lock);
> -			filp_close(file, files);
> +			filp_close(file, owner);
>  			cond_resched();
>  			spin_lock(&files->file_lock);
>  		}
> @@ -1080,6 +1084,7 @@ static int do_dup2(struct files_struct *files,
>  	struct file *file, unsigned fd, unsigned flags)
>  __releases(&files->file_lock)
>  {
> +	fl_owner_t owner = file_lock_make_thread_owner(files);
>  	struct file *tofree;
>  	struct fdtable *fdt;
>  
> @@ -1111,7 +1116,7 @@ __releases(&files->file_lock)
>  	spin_unlock(&files->file_lock);
>  
>  	if (tofree)
> -		filp_close(tofree, files);
> +		filp_close(tofree, owner);
>  
>  	return fd;
>  
> diff --git a/fs/locks.c b/fs/locks.c
> index 607f94a0e789..e8b67f87e0ee 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -331,6 +331,8 @@ EXPORT_SYMBOL_GPL(locks_owner_has_blockers);
>  /* Free a lock which is not in use. */
>  void locks_free_lock(struct file_lock *fl)
>  {
> +	if (fl->fl_file && file_lock_is_thread_owner(fl->fl_owner))
> +		fput(fl->fl_file);
>  	locks_release_private(fl);
>  	kmem_cache_free(filelock_cache, fl);
>  }
> @@ -384,7 +386,10 @@ void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
>  
>  	locks_copy_conflock(new, fl);
>  
> -	new->fl_file = fl->fl_file;
> +	if (file_lock_is_thread_owner(new->fl_owner))
> +		new->fl_file = get_file(fl->fl_file);
> +	else
> +		new->fl_file = fl->fl_file;
>  	new->fl_ops = fl->fl_ops;
>  
>  	if (fl->fl_ops) {
> @@ -488,13 +493,14 @@ static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
>  	} else
>  		fl->fl_end = OFFSET_MAX;
>  
> -	fl->fl_owner = current->files;
> +	fl->fl_owner = file_lock_make_thread_owner(current->files);
>  	fl->fl_pid = current->tgid;
> -	fl->fl_file = filp;
> +	fl->fl_file = get_file(filp);
>  	fl->fl_flags = FL_POSIX;
>  	fl->fl_ops = NULL;
>  	fl->fl_lmops = NULL;
>  
> +
>  	return assign_type(fl, l->l_type);
>  }
>  
> @@ -2243,6 +2249,7 @@ int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock *flock)
>  
>  		fl->fl_flags |= FL_OFDLCK;
>  		fl->fl_owner = filp;
> +		fput(filp);
>  	}
>  
>  	error = vfs_test_lock(filp, fl);
> @@ -2376,6 +2383,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
>  		cmd = F_SETLK;
>  		file_lock->fl_flags |= FL_OFDLCK;
>  		file_lock->fl_owner = filp;
> +		fput(filp);
>  		break;
>  	case F_OFD_SETLKW:
>  		error = -EINVAL;
> @@ -2385,6 +2393,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
>  		cmd = F_SETLKW;
>  		file_lock->fl_flags |= FL_OFDLCK;
>  		file_lock->fl_owner = filp;
> +		fput(filp);
>  		fallthrough;
>  	case F_SETLKW:
>  		file_lock->fl_flags |= FL_SLEEP;
> @@ -2450,6 +2459,7 @@ int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 *flock)
>  		cmd = F_GETLK64;
>  		fl->fl_flags |= FL_OFDLCK;
>  		fl->fl_owner = filp;
> +		fput(filp);
>  	}
>  
>  	error = vfs_test_lock(filp, fl);
> @@ -2499,6 +2509,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
>  		cmd = F_SETLK64;
>  		file_lock->fl_flags |= FL_OFDLCK;
>  		file_lock->fl_owner = filp;
> +		fput(filp);
>  		break;
>  	case F_OFD_SETLKW:
>  		error = -EINVAL;
> @@ -2508,6 +2519,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
>  		cmd = F_SETLKW64;
>  		file_lock->fl_flags |= FL_OFDLCK;
>  		file_lock->fl_owner = filp;
> +		fput(filp);
>  		fallthrough;
>  	case F_SETLKW64:
>  		file_lock->fl_flags |= FL_SLEEP;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index e654435f1651..d7d81962a863 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1028,6 +1028,20 @@ static inline struct file *get_file(struct file *f)
>  /* legacy typedef, should eventually be removed */
>  typedef void *fl_owner_t;
>  
> +/*
> + * Set the last significant bit to 1 to mark that
> + * we have get a reference of the fl->fl_file.
> + */
> +static inline fl_owner_t file_lock_make_thread_owner(fl_owner_t owner)
> +{
> +	return (fl_owner_t)((unsigned long)owner | 1UL);
> +}
> +
> +static inline bool file_lock_is_thread_owner(fl_owner_t owner)
> +{
> +	return ((unsigned long)owner & 1UL);
> +}
> +
>  struct file_lock;
>  
>  struct file_lock_operations {
> diff --git a/io_uring/openclose.c b/io_uring/openclose.c
> index 67178e4bb282..5a12cdf7f8d0 100644
> --- a/io_uring/openclose.c
> +++ b/io_uring/openclose.c
> @@ -212,6 +212,7 @@ int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>  int io_close(struct io_kiocb *req, unsigned int issue_flags)
>  {
>  	struct files_struct *files = current->files;
> +	fl_owner_t owner = file_lock_make_thread_owner(files);
>  	struct io_close *close = io_kiocb_to_cmd(req, struct io_close);
>  	struct fdtable *fdt;
>  	struct file *file;
> @@ -247,7 +248,7 @@ int io_close(struct io_kiocb *req, unsigned int issue_flags)
>  		goto err;
>  
>  	/* No ->flush() or already async, safely close from here */
> -	ret = filp_close(file, current->files);
> +	ret = filp_close(file, owner);
>  err:
>  	if (ret < 0)
>  		req_set_fail(req);

I think this is the wrong approach to fixing this. It also looks like
you could hit a similar problem with OFD locks and this patch wouldn't
address that issue.

The real bug seems to be that ceph_fl_release_lock dereferences fl_file,
at a point when it shouldn't rely on that being valid. Most filesystems
stash some info in fl->fl_u if they need to do bookkeeping after
releasing a lock. Perhaps ceph should be doing something similar?
-- 
Jeff Layton <jlayton@kernel.org>

Re: [RFC PATCH] fs/lock: increase the filp's reference for Posix-style locks

[Xiubo Li]

On 07/11/2022 18:33, Jeff Layton wrote:
> On Mon, 2022-11-07 at 17:52 +0800, xiubli@redhat.com wrote:
>> From: Xiubo Li <xiubli@redhat.com>
>>
>> When closing the file descripters in parallel in multiple threads,
>> who are sharing the same file descripters, the filp_close() will
>> remove all the Posix-style locks. But if two threads both calling
>> the filp_close() it may race and cause use-after-free crash:
>>
>>   PID: 327771   TASK: ffff952aa1db3180  CPU: 8    COMMAND: "db2fmp"
>>    #0 [ffff95202f33b960] machine_kexec at ffffffff890662f4
>>    #1 [ffff95202f33b9c0] __crash_kexec at ffffffff89122b82
>>    #2 [ffff95202f33ba90] crash_kexec at ffffffff89122c70
>>    #3 [ffff95202f33baa8] oops_end at ffffffff89791798
>>    #4 [ffff95202f33bad0] no_context at ffffffff89075d14
>>    #5 [ffff95202f33bb20] __bad_area_nosemaphore at ffffffff89075fe2
>>    #6 [ffff95202f33bb70] bad_area_nosemaphore at ffffffff89076104
>>    #7 [ffff95202f33bb80] __do_page_fault at ffffffff89794750
>>    #8 [ffff95202f33bbf0] do_page_fault at ffffffff89794975
>>    #9 [ffff95202f33bc20] page_fault at ffffffff89790778
>>       [exception RIP: ceph_fl_release_lock+20]
>>       RIP: ffffffffc08247a4  RSP: ffff95202f33bcd0  RFLAGS: 00010286
>>       RAX: ffff952d4ebd8a00  RBX: 0000000000000000  RCX: dead000000000200
>>       RDX: ffff95202f33bd60  RSI: ffff95202f33bd60  RDI: ffff9526b6ac5b00
>>       RBP: ffff95202f33bce0   R8: ffff9526b6ac5b18   R9: ffffffffc083c368
>>       R10: 0000000000001109  R11: 0000000000000000  R12: ffff95202f33bd60
>>       R13: ffff9526b6ac5b00  R14: 0000000000000000  R15: 0000000000000000
>>       ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
>>   #10 [ffff95202f33bce8] locks_release_private at ffffffff892ab3d7
>>   #11 [ffff95202f33bd00] locks_free_lock at ffffffff892ac34d
>>   #12 [ffff95202f33bd18] locks_dispose_list at ffffffff892ac44b
>>   #13 [ffff95202f33bd40] __posix_lock_file at ffffffff892acdfa
>>   #14 [ffff95202f33bda8] posix_lock_file at ffffffff892ad146
>>   #15 [ffff95202f33bdb8] ceph_lock at ffffffffc0824e8a [ceph]
>>   #16 [ffff95202f33bdf8] vfs_lock_file at ffffffff892ad185
>>   #17 [ffff95202f33be08] locks_remove_posix at ffffffff892ad239
>>   #18 [ffff95202f33bee0] locks_remove_posix at ffffffff892ad2a0
>>   #19 [ffff95202f33bef0] filp_close at ffffffff8924baa6
>>   #20 [ffff95202f33bf18] __close_fd at ffffffff8926f89c
>>   #21 [ffff95202f33bf40] sys_close at ffffffff8924d503
>>   #22 [ffff95202f33bf50] system_call_fastpath at ffffffff89799f92
>>       RIP: 00007f806ec446ab  RSP: 00007f80517f0d90  RFLAGS: 00010206
>>       RAX: 0000000000000003  RBX: 00007f8030001a20  RCX: 00007f80300386b0
>>       RDX: 00007f806ef0d880  RSI: 0000000000000001  RDI: 0000000000000006
>>       RBP: 00007f806ef0e3c0   R8: 00007f80517fa700   R9: 0000000000000000
>>       R10: 0000000000000000  R11: 0000000000000206  R12: 0000000000000000
>>       R13: 00007f80300035b0  R14: 00007f80517f1104  R15: 000000000000006c
>>       ORIG_RAX: 0000000000000003  CS: 0033  SS: 002b
>>
>> We need to make sure that the filp in the file_lock shouldn't be
>> release when any file_lock is still referring to it.
>>
>> For the Posix-style locks, whose owner will be the thread ids, we
>> will increase the filp's reference.
>>
>> URL: https://tracker.ceph.com/issues/57986
>> Signed-off-by: Xiubo Li <xiubli@redhat.com>
>> ---
>>   drivers/android/binder.c |  2 +-
>>   fs/file.c                | 15 ++++++++++-----
>>   fs/locks.c               | 18 +++++++++++++++---
>>   include/linux/fs.h       | 14 ++++++++++++++
>>   io_uring/openclose.c     |  3 ++-
>>   5 files changed, 42 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
>> index 880224ec6abb..03692564d940 100644
>> --- a/drivers/android/binder.c
>> +++ b/drivers/android/binder.c
>> @@ -1924,7 +1924,7 @@ static void binder_deferred_fd_close(int fd)
>>   	if (twcb->file) {
>>   		// pin it until binder_do_fd_close(); see comments there
>>   		get_file(twcb->file);
>> -		filp_close(twcb->file, current->files);
>> +		filp_close(twcb->file, file_lock_make_thread_owner(current->files));
>>   		task_work_add(current, &twcb->twork, TWA_RESUME);
>>   	} else {
>>   		kfree(twcb);
>> diff --git a/fs/file.c b/fs/file.c
>> index 5f9c802a5d8d..39ad8e74a8d9 100644
>> --- a/fs/file.c
>> +++ b/fs/file.c
>> @@ -417,6 +417,7 @@ static struct fdtable *close_files(struct files_struct * files)
>>   	 * files structure.
>>   	 */
>>   	struct fdtable *fdt = rcu_dereference_raw(files->fdt);
>> +	fl_owner_t owner = file_lock_make_thread_owner(files);
>>   	unsigned int i, j = 0;
>>   
>>   	for (;;) {
>> @@ -429,7 +430,7 @@ static struct fdtable *close_files(struct files_struct * files)
>>   			if (set & 1) {
>>   				struct file * file = xchg(&fdt->fd[i], NULL);
>>   				if (file) {
>> -					filp_close(file, files);
>> +					filp_close(file, owner);
>>   					cond_resched();
>>   				}
>>   			}
>> @@ -653,6 +654,7 @@ static struct file *pick_file(struct files_struct *files, unsigned fd)
>>   int close_fd(unsigned fd)
>>   {
>>   	struct files_struct *files = current->files;
>> +	fl_owner_t owner = file_lock_make_thread_owner(files);
>>   	struct file *file;
>>   
>>   	spin_lock(&files->file_lock);
>> @@ -661,7 +663,7 @@ int close_fd(unsigned fd)
>>   	if (!file)
>>   		return -EBADF;
>>   
>> -	return filp_close(file, files);
>> +	return filp_close(file, owner);
>>   }
>>   EXPORT_SYMBOL(close_fd); /* for ksys_close() */
>>   
>> @@ -695,6 +697,7 @@ static inline void __range_cloexec(struct files_struct *cur_fds,
>>   static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
>>   				 unsigned int max_fd)
>>   {
>> +	fl_owner_t owner = file_lock_make_thread_owner(cur_fds);
>>   	unsigned n;
>>   
>>   	rcu_read_lock();
>> @@ -711,7 +714,7 @@ static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
>>   
>>   		if (file) {
>>   			/* found a valid file to close */
>> -			filp_close(file, cur_fds);
>> +			filp_close(file, owner);
>>   			cond_resched();
>>   		}
>>   	}
>> @@ -816,6 +819,7 @@ struct file *close_fd_get_file(unsigned int fd)
>>   
>>   void do_close_on_exec(struct files_struct *files)
>>   {
>> +	fl_owner_t owner = file_lock_make_thread_owner(files);
>>   	unsigned i;
>>   	struct fdtable *fdt;
>>   
>> @@ -841,7 +845,7 @@ void do_close_on_exec(struct files_struct *files)
>>   			rcu_assign_pointer(fdt->fd[fd], NULL);
>>   			__put_unused_fd(files, fd);
>>   			spin_unlock(&files->file_lock);
>> -			filp_close(file, files);
>> +			filp_close(file, owner);
>>   			cond_resched();
>>   			spin_lock(&files->file_lock);
>>   		}
>> @@ -1080,6 +1084,7 @@ static int do_dup2(struct files_struct *files,
>>   	struct file *file, unsigned fd, unsigned flags)
>>   __releases(&files->file_lock)
>>   {
>> +	fl_owner_t owner = file_lock_make_thread_owner(files);
>>   	struct file *tofree;
>>   	struct fdtable *fdt;
>>   
>> @@ -1111,7 +1116,7 @@ __releases(&files->file_lock)
>>   	spin_unlock(&files->file_lock);
>>   
>>   	if (tofree)
>> -		filp_close(tofree, files);
>> +		filp_close(tofree, owner);
>>   
>>   	return fd;
>>   
>> diff --git a/fs/locks.c b/fs/locks.c
>> index 607f94a0e789..e8b67f87e0ee 100644
>> --- a/fs/locks.c
>> +++ b/fs/locks.c
>> @@ -331,6 +331,8 @@ EXPORT_SYMBOL_GPL(locks_owner_has_blockers);
>>   /* Free a lock which is not in use. */
>>   void locks_free_lock(struct file_lock *fl)
>>   {
>> +	if (fl->fl_file && file_lock_is_thread_owner(fl->fl_owner))
>> +		fput(fl->fl_file);
>>   	locks_release_private(fl);
>>   	kmem_cache_free(filelock_cache, fl);
>>   }
>> @@ -384,7 +386,10 @@ void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
>>   
>>   	locks_copy_conflock(new, fl);
>>   
>> -	new->fl_file = fl->fl_file;
>> +	if (file_lock_is_thread_owner(new->fl_owner))
>> +		new->fl_file = get_file(fl->fl_file);
>> +	else
>> +		new->fl_file = fl->fl_file;
>>   	new->fl_ops = fl->fl_ops;
>>   
>>   	if (fl->fl_ops) {
>> @@ -488,13 +493,14 @@ static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
>>   	} else
>>   		fl->fl_end = OFFSET_MAX;
>>   
>> -	fl->fl_owner = current->files;
>> +	fl->fl_owner = file_lock_make_thread_owner(current->files);
>>   	fl->fl_pid = current->tgid;
>> -	fl->fl_file = filp;
>> +	fl->fl_file = get_file(filp);
>>   	fl->fl_flags = FL_POSIX;
>>   	fl->fl_ops = NULL;
>>   	fl->fl_lmops = NULL;
>>   
>> +
>>   	return assign_type(fl, l->l_type);
>>   }
>>   
>> @@ -2243,6 +2249,7 @@ int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock *flock)
>>   
>>   		fl->fl_flags |= FL_OFDLCK;
>>   		fl->fl_owner = filp;
>> +		fput(filp);
>>   	}
>>   
>>   	error = vfs_test_lock(filp, fl);
>> @@ -2376,6 +2383,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
>>   		cmd = F_SETLK;
>>   		file_lock->fl_flags |= FL_OFDLCK;
>>   		file_lock->fl_owner = filp;
>> +		fput(filp);
>>   		break;
>>   	case F_OFD_SETLKW:
>>   		error = -EINVAL;
>> @@ -2385,6 +2393,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
>>   		cmd = F_SETLKW;
>>   		file_lock->fl_flags |= FL_OFDLCK;
>>   		file_lock->fl_owner = filp;
>> +		fput(filp);
>>   		fallthrough;
>>   	case F_SETLKW:
>>   		file_lock->fl_flags |= FL_SLEEP;
>> @@ -2450,6 +2459,7 @@ int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 *flock)
>>   		cmd = F_GETLK64;
>>   		fl->fl_flags |= FL_OFDLCK;
>>   		fl->fl_owner = filp;
>> +		fput(filp);
>>   	}
>>   
>>   	error = vfs_test_lock(filp, fl);
>> @@ -2499,6 +2509,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
>>   		cmd = F_SETLK64;
>>   		file_lock->fl_flags |= FL_OFDLCK;
>>   		file_lock->fl_owner = filp;
>> +		fput(filp);
>>   		break;
>>   	case F_OFD_SETLKW:
>>   		error = -EINVAL;
>> @@ -2508,6 +2519,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
>>   		cmd = F_SETLKW64;
>>   		file_lock->fl_flags |= FL_OFDLCK;
>>   		file_lock->fl_owner = filp;
>> +		fput(filp);
>>   		fallthrough;
>>   	case F_SETLKW64:
>>   		file_lock->fl_flags |= FL_SLEEP;
>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index e654435f1651..d7d81962a863 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -1028,6 +1028,20 @@ static inline struct file *get_file(struct file *f)
>>   /* legacy typedef, should eventually be removed */
>>   typedef void *fl_owner_t;
>>   
>> +/*
>> + * Set the last significant bit to 1 to mark that
>> + * we have get a reference of the fl->fl_file.
>> + */
>> +static inline fl_owner_t file_lock_make_thread_owner(fl_owner_t owner)
>> +{
>> +	return (fl_owner_t)((unsigned long)owner | 1UL);
>> +}
>> +
>> +static inline bool file_lock_is_thread_owner(fl_owner_t owner)
>> +{
>> +	return ((unsigned long)owner & 1UL);
>> +}
>> +
>>   struct file_lock;
>>   
>>   struct file_lock_operations {
>> diff --git a/io_uring/openclose.c b/io_uring/openclose.c
>> index 67178e4bb282..5a12cdf7f8d0 100644
>> --- a/io_uring/openclose.c
>> +++ b/io_uring/openclose.c
>> @@ -212,6 +212,7 @@ int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>>   int io_close(struct io_kiocb *req, unsigned int issue_flags)
>>   {
>>   	struct files_struct *files = current->files;
>> +	fl_owner_t owner = file_lock_make_thread_owner(files);
>>   	struct io_close *close = io_kiocb_to_cmd(req, struct io_close);
>>   	struct fdtable *fdt;
>>   	struct file *file;
>> @@ -247,7 +248,7 @@ int io_close(struct io_kiocb *req, unsigned int issue_flags)
>>   		goto err;
>>   
>>   	/* No ->flush() or already async, safely close from here */
>> -	ret = filp_close(file, current->files);
>> +	ret = filp_close(file, owner);
>>   err:
>>   	if (ret < 0)
>>   		req_set_fail(req);
> I think this is the wrong approach to fixing this. It also looks like
> you could hit a similar problem with OFD locks and this patch wouldn't
> address that issue.

For the OFD locks they will set the 'file' struct as the owner just as 
the flock does, it should be okay and I don't think it has this issue if 
my understanding is correct here.

> The real bug seems to be that ceph_fl_release_lock dereferences fl_file,
> at a point when it shouldn't rely on that being valid. Most filesystems
> stash some info in fl->fl_u if they need to do bookkeeping after
> releasing a lock. Perhaps ceph should be doing something similar?

This is the 'filp' memory in filp_close(filp, ...):

crash> file.f_path.dentry,f_inode 0xffff952d7ab46200
   f_path.dentry = 0xffff9521b121cb40
   f_inode = 0xffff951f3ea33550,

We can see the 'f_inode' is pointing to the correct inode memory.


While later in 'ceph_fl_release_lock()':

41 static void ceph_fl_release_lock(struct file_lock *fl)
42 {
43     struct ceph_file_info *fi = fl->fl_file->private_data;
44     struct inode *inode = file_inode(fl->fl_file);
45     struct ceph_inode_info *ci = ceph_inode(inode);
46     atomic_dec(&fi->num_locks);
47     if (atomic_dec_and_test(&ci->i_filelock_ref)) {
48         /* clear error when all locks are released */
49         spin_lock(&ci->i_ceph_lock);
50         ci->i_ceph_flags &= ~CEPH_I_ERROR_FILELOCK;
51         spin_unlock(&ci->i_ceph_lock);
52     }
53 }

It crashed in Line#47 and the 'fl->fl_file' memory is:

crash> file.f_path.dentry,f_inode 0xffff952d4ebd8a00
   f_path.dentry = 0x0
   f_inode = 0x0,

Please NOTE: the 'filp' and 'fl->fl_file' are two different 'file struct'.

Can we fix this by using 'fl->fl_u' here ?

I was also thinking I could just call the 'get_file(file)' in 
ceph_lock() and then in ceph_fl_release_lock() release the reference 
counter. How about this ?

Thanks!

- Xiubo

Re: [RFC PATCH] fs/lock: increase the filp's reference for Posix-style locks

[Jeff Layton]

On Mon, 2022-11-07 at 20:03 +0800, Xiubo Li wrote:
> On 07/11/2022 18:33, Jeff Layton wrote:
> > On Mon, 2022-11-07 at 17:52 +0800, xiubli@redhat.com wrote:
> > > From: Xiubo Li <xiubli@redhat.com>
> > > 
> > > When closing the file descripters in parallel in multiple threads,
> > > who are sharing the same file descripters, the filp_close() will
> > > remove all the Posix-style locks. But if two threads both calling
> > > the filp_close() it may race and cause use-after-free crash:
> > > 
> > >   PID: 327771   TASK: ffff952aa1db3180  CPU: 8    COMMAND: "db2fmp"
> > >    #0 [ffff95202f33b960] machine_kexec at ffffffff890662f4
> > >    #1 [ffff95202f33b9c0] __crash_kexec at ffffffff89122b82
> > >    #2 [ffff95202f33ba90] crash_kexec at ffffffff89122c70
> > >    #3 [ffff95202f33baa8] oops_end at ffffffff89791798
> > >    #4 [ffff95202f33bad0] no_context at ffffffff89075d14
> > >    #5 [ffff95202f33bb20] __bad_area_nosemaphore at ffffffff89075fe2
> > >    #6 [ffff95202f33bb70] bad_area_nosemaphore at ffffffff89076104
> > >    #7 [ffff95202f33bb80] __do_page_fault at ffffffff89794750
> > >    #8 [ffff95202f33bbf0] do_page_fault at ffffffff89794975
> > >    #9 [ffff95202f33bc20] page_fault at ffffffff89790778
> > >       [exception RIP: ceph_fl_release_lock+20]
> > >       RIP: ffffffffc08247a4  RSP: ffff95202f33bcd0  RFLAGS: 00010286
> > >       RAX: ffff952d4ebd8a00  RBX: 0000000000000000  RCX: dead000000000200
> > >       RDX: ffff95202f33bd60  RSI: ffff95202f33bd60  RDI: ffff9526b6ac5b00
> > >       RBP: ffff95202f33bce0   R8: ffff9526b6ac5b18   R9: ffffffffc083c368
> > >       R10: 0000000000001109  R11: 0000000000000000  R12: ffff95202f33bd60
> > >       R13: ffff9526b6ac5b00  R14: 0000000000000000  R15: 0000000000000000
> > >       ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
> > >   #10 [ffff95202f33bce8] locks_release_private at ffffffff892ab3d7
> > >   #11 [ffff95202f33bd00] locks_free_lock at ffffffff892ac34d
> > >   #12 [ffff95202f33bd18] locks_dispose_list at ffffffff892ac44b
> > >   #13 [ffff95202f33bd40] __posix_lock_file at ffffffff892acdfa
> > >   #14 [ffff95202f33bda8] posix_lock_file at ffffffff892ad146
> > >   #15 [ffff95202f33bdb8] ceph_lock at ffffffffc0824e8a [ceph]
> > >   #16 [ffff95202f33bdf8] vfs_lock_file at ffffffff892ad185
> > >   #17 [ffff95202f33be08] locks_remove_posix at ffffffff892ad239
> > >   #18 [ffff95202f33bee0] locks_remove_posix at ffffffff892ad2a0
> > >   #19 [ffff95202f33bef0] filp_close at ffffffff8924baa6
> > >   #20 [ffff95202f33bf18] __close_fd at ffffffff8926f89c
> > >   #21 [ffff95202f33bf40] sys_close at ffffffff8924d503
> > >   #22 [ffff95202f33bf50] system_call_fastpath at ffffffff89799f92
> > >       RIP: 00007f806ec446ab  RSP: 00007f80517f0d90  RFLAGS: 00010206
> > >       RAX: 0000000000000003  RBX: 00007f8030001a20  RCX: 00007f80300386b0
> > >       RDX: 00007f806ef0d880  RSI: 0000000000000001  RDI: 0000000000000006
> > >       RBP: 00007f806ef0e3c0   R8: 00007f80517fa700   R9: 0000000000000000
> > >       R10: 0000000000000000  R11: 0000000000000206  R12: 0000000000000000
> > >       R13: 00007f80300035b0  R14: 00007f80517f1104  R15: 000000000000006c
> > >       ORIG_RAX: 0000000000000003  CS: 0033  SS: 002b
> > > 
> > > We need to make sure that the filp in the file_lock shouldn't be
> > > release when any file_lock is still referring to it.
> > > 
> > > For the Posix-style locks, whose owner will be the thread ids, we
> > > will increase the filp's reference.
> > > 
> > > URL: https://tracker.ceph.com/issues/57986
> > > Signed-off-by: Xiubo Li <xiubli@redhat.com>
> > > ---
> > >   drivers/android/binder.c |  2 +-
> > >   fs/file.c                | 15 ++++++++++-----
> > >   fs/locks.c               | 18 +++++++++++++++---
> > >   include/linux/fs.h       | 14 ++++++++++++++
> > >   io_uring/openclose.c     |  3 ++-
> > >   5 files changed, 42 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> > > index 880224ec6abb..03692564d940 100644
> > > --- a/drivers/android/binder.c
> > > +++ b/drivers/android/binder.c
> > > @@ -1924,7 +1924,7 @@ static void binder_deferred_fd_close(int fd)
> > >   	if (twcb->file) {
> > >   		// pin it until binder_do_fd_close(); see comments there
> > >   		get_file(twcb->file);
> > > -		filp_close(twcb->file, current->files);
> > > +		filp_close(twcb->file, file_lock_make_thread_owner(current->files));
> > >   		task_work_add(current, &twcb->twork, TWA_RESUME);
> > >   	} else {
> > >   		kfree(twcb);
> > > diff --git a/fs/file.c b/fs/file.c
> > > index 5f9c802a5d8d..39ad8e74a8d9 100644
> > > --- a/fs/file.c
> > > +++ b/fs/file.c
> > > @@ -417,6 +417,7 @@ static struct fdtable *close_files(struct files_struct * files)
> > >   	 * files structure.
> > >   	 */
> > >   	struct fdtable *fdt = rcu_dereference_raw(files->fdt);
> > > +	fl_owner_t owner = file_lock_make_thread_owner(files);
> > >   	unsigned int i, j = 0;
> > >   
> > >   	for (;;) {
> > > @@ -429,7 +430,7 @@ static struct fdtable *close_files(struct files_struct * files)
> > >   			if (set & 1) {
> > >   				struct file * file = xchg(&fdt->fd[i], NULL);
> > >   				if (file) {
> > > -					filp_close(file, files);
> > > +					filp_close(file, owner);
> > >   					cond_resched();
> > >   				}
> > >   			}
> > > @@ -653,6 +654,7 @@ static struct file *pick_file(struct files_struct *files, unsigned fd)
> > >   int close_fd(unsigned fd)
> > >   {
> > >   	struct files_struct *files = current->files;
> > > +	fl_owner_t owner = file_lock_make_thread_owner(files);
> > >   	struct file *file;
> > >   
> > >   	spin_lock(&files->file_lock);
> > > @@ -661,7 +663,7 @@ int close_fd(unsigned fd)
> > >   	if (!file)
> > >   		return -EBADF;
> > >   
> > > -	return filp_close(file, files);
> > > +	return filp_close(file, owner);
> > >   }
> > >   EXPORT_SYMBOL(close_fd); /* for ksys_close() */
> > >   
> > > @@ -695,6 +697,7 @@ static inline void __range_cloexec(struct files_struct *cur_fds,
> > >   static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
> > >   				 unsigned int max_fd)
> > >   {
> > > +	fl_owner_t owner = file_lock_make_thread_owner(cur_fds);
> > >   	unsigned n;
> > >   
> > >   	rcu_read_lock();
> > > @@ -711,7 +714,7 @@ static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
> > >   
> > >   		if (file) {
> > >   			/* found a valid file to close */
> > > -			filp_close(file, cur_fds);
> > > +			filp_close(file, owner);
> > >   			cond_resched();
> > >   		}
> > >   	}
> > > @@ -816,6 +819,7 @@ struct file *close_fd_get_file(unsigned int fd)
> > >   
> > >   void do_close_on_exec(struct files_struct *files)
> > >   {
> > > +	fl_owner_t owner = file_lock_make_thread_owner(files);
> > >   	unsigned i;
> > >   	struct fdtable *fdt;
> > >   
> > > @@ -841,7 +845,7 @@ void do_close_on_exec(struct files_struct *files)
> > >   			rcu_assign_pointer(fdt->fd[fd], NULL);
> > >   			__put_unused_fd(files, fd);
> > >   			spin_unlock(&files->file_lock);
> > > -			filp_close(file, files);
> > > +			filp_close(file, owner);
> > >   			cond_resched();
> > >   			spin_lock(&files->file_lock);
> > >   		}
> > > @@ -1080,6 +1084,7 @@ static int do_dup2(struct files_struct *files,
> > >   	struct file *file, unsigned fd, unsigned flags)
> > >   __releases(&files->file_lock)
> > >   {
> > > +	fl_owner_t owner = file_lock_make_thread_owner(files);
> > >   	struct file *tofree;
> > >   	struct fdtable *fdt;
> > >   
> > > @@ -1111,7 +1116,7 @@ __releases(&files->file_lock)
> > >   	spin_unlock(&files->file_lock);
> > >   
> > >   	if (tofree)
> > > -		filp_close(tofree, files);
> > > +		filp_close(tofree, owner);
> > >   
> > >   	return fd;
> > >   
> > > diff --git a/fs/locks.c b/fs/locks.c
> > > index 607f94a0e789..e8b67f87e0ee 100644
> > > --- a/fs/locks.c
> > > +++ b/fs/locks.c
> > > @@ -331,6 +331,8 @@ EXPORT_SYMBOL_GPL(locks_owner_has_blockers);
> > >   /* Free a lock which is not in use. */
> > >   void locks_free_lock(struct file_lock *fl)
> > >   {
> > > +	if (fl->fl_file && file_lock_is_thread_owner(fl->fl_owner))
> > > +		fput(fl->fl_file);
> > >   	locks_release_private(fl);
> > >   	kmem_cache_free(filelock_cache, fl);
> > >   }
> > > @@ -384,7 +386,10 @@ void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
> > >   
> > >   	locks_copy_conflock(new, fl);
> > >   
> > > -	new->fl_file = fl->fl_file;
> > > +	if (file_lock_is_thread_owner(new->fl_owner))
> > > +		new->fl_file = get_file(fl->fl_file);
> > > +	else
> > > +		new->fl_file = fl->fl_file;
> > >   	new->fl_ops = fl->fl_ops;
> > >   
> > >   	if (fl->fl_ops) {
> > > @@ -488,13 +493,14 @@ static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
> > >   	} else
> > >   		fl->fl_end = OFFSET_MAX;
> > >   
> > > -	fl->fl_owner = current->files;
> > > +	fl->fl_owner = file_lock_make_thread_owner(current->files);
> > >   	fl->fl_pid = current->tgid;
> > > -	fl->fl_file = filp;
> > > +	fl->fl_file = get_file(filp);
> > >   	fl->fl_flags = FL_POSIX;
> > >   	fl->fl_ops = NULL;
> > >   	fl->fl_lmops = NULL;
> > >   
> > > +
> > >   	return assign_type(fl, l->l_type);
> > >   }
> > >   
> > > @@ -2243,6 +2249,7 @@ int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock *flock)
> > >   
> > >   		fl->fl_flags |= FL_OFDLCK;
> > >   		fl->fl_owner = filp;
> > > +		fput(filp);
> > >   	}
> > >   
> > >   	error = vfs_test_lock(filp, fl);
> > > @@ -2376,6 +2383,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
> > >   		cmd = F_SETLK;
> > >   		file_lock->fl_flags |= FL_OFDLCK;
> > >   		file_lock->fl_owner = filp;
> > > +		fput(filp);
> > >   		break;
> > >   	case F_OFD_SETLKW:
> > >   		error = -EINVAL;
> > > @@ -2385,6 +2393,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
> > >   		cmd = F_SETLKW;
> > >   		file_lock->fl_flags |= FL_OFDLCK;
> > >   		file_lock->fl_owner = filp;
> > > +		fput(filp);
> > >   		fallthrough;
> > >   	case F_SETLKW:
> > >   		file_lock->fl_flags |= FL_SLEEP;
> > > @@ -2450,6 +2459,7 @@ int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 *flock)
> > >   		cmd = F_GETLK64;
> > >   		fl->fl_flags |= FL_OFDLCK;
> > >   		fl->fl_owner = filp;
> > > +		fput(filp);
> > >   	}
> > >   
> > >   	error = vfs_test_lock(filp, fl);
> > > @@ -2499,6 +2509,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
> > >   		cmd = F_SETLK64;
> > >   		file_lock->fl_flags |= FL_OFDLCK;
> > >   		file_lock->fl_owner = filp;
> > > +		fput(filp);
> > >   		break;
> > >   	case F_OFD_SETLKW:
> > >   		error = -EINVAL;
> > > @@ -2508,6 +2519,7 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
> > >   		cmd = F_SETLKW64;
> > >   		file_lock->fl_flags |= FL_OFDLCK;
> > >   		file_lock->fl_owner = filp;
> > > +		fput(filp);
> > >   		fallthrough;
> > >   	case F_SETLKW64:
> > >   		file_lock->fl_flags |= FL_SLEEP;
> > > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > > index e654435f1651..d7d81962a863 100644
> > > --- a/include/linux/fs.h
> > > +++ b/include/linux/fs.h
> > > @@ -1028,6 +1028,20 @@ static inline struct file *get_file(struct file *f)
> > >   /* legacy typedef, should eventually be removed */
> > >   typedef void *fl_owner_t;
> > >   
> > > +/*
> > > + * Set the last significant bit to 1 to mark that
> > > + * we have get a reference of the fl->fl_file.
> > > + */
> > > +static inline fl_owner_t file_lock_make_thread_owner(fl_owner_t owner)
> > > +{
> > > +	return (fl_owner_t)((unsigned long)owner | 1UL);
> > > +}
> > > +
> > > +static inline bool file_lock_is_thread_owner(fl_owner_t owner)
> > > +{
> > > +	return ((unsigned long)owner & 1UL);
> > > +}
> > > +
> > >   struct file_lock;
> > >   
> > >   struct file_lock_operations {
> > > diff --git a/io_uring/openclose.c b/io_uring/openclose.c
> > > index 67178e4bb282..5a12cdf7f8d0 100644
> > > --- a/io_uring/openclose.c
> > > +++ b/io_uring/openclose.c
> > > @@ -212,6 +212,7 @@ int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
> > >   int io_close(struct io_kiocb *req, unsigned int issue_flags)
> > >   {
> > >   	struct files_struct *files = current->files;
> > > +	fl_owner_t owner = file_lock_make_thread_owner(files);
> > >   	struct io_close *close = io_kiocb_to_cmd(req, struct io_close);
> > >   	struct fdtable *fdt;
> > >   	struct file *file;
> > > @@ -247,7 +248,7 @@ int io_close(struct io_kiocb *req, unsigned int issue_flags)
> > >   		goto err;
> > >   
> > >   	/* No ->flush() or already async, safely close from here */
> > > -	ret = filp_close(file, current->files);
> > > +	ret = filp_close(file, owner);
> > >   err:
> > >   	if (ret < 0)
> > >   		req_set_fail(req);
> > I think this is the wrong approach to fixing this. It also looks like
> > you could hit a similar problem with OFD locks and this patch wouldn't
> > address that issue.
> 
> For the OFD locks they will set the 'file' struct as the owner just as 
> the flock does, it should be okay and I don't think it has this issue if 
> my understanding is correct here.
> 

They set the the owner to "file", but they don't hold a reference to it.
With OFD locks, the file is what holds references to the lock, not the
reverse.

> > The real bug seems to be that ceph_fl_release_lock dereferences fl_file,
> > at a point when it shouldn't rely on that being valid. Most filesystems
> > stash some info in fl->fl_u if they need to do bookkeeping after
> > releasing a lock. Perhaps ceph should be doing something similar?
> 
> This is the 'filp' memory in filp_close(filp, ...):
> 
> crash> file.f_path.dentry,f_inode 0xffff952d7ab46200
>    f_path.dentry = 0xffff9521b121cb40
>    f_inode = 0xffff951f3ea33550,
> 
> We can see the 'f_inode' is pointing to the correct inode memory.
> 
> 
> 
> While later in 'ceph_fl_release_lock()':
> 
> 41 static void ceph_fl_release_lock(struct file_lock *fl)
> 42 {
> 43     struct ceph_file_info *fi = fl->fl_file->private_data;
> 44     struct inode *inode = file_inode(fl->fl_file);
> 45     struct ceph_inode_info *ci = ceph_inode(inode);
> 46     atomic_dec(&fi->num_locks);
> 47     if (atomic_dec_and_test(&ci->i_filelock_ref)) {
> 48         /* clear error when all locks are released */
> 49         spin_lock(&ci->i_ceph_lock);
> 50         ci->i_ceph_flags &= ~CEPH_I_ERROR_FILELOCK;
> 51         spin_unlock(&ci->i_ceph_lock);
> 52     }
> 53 }
> 

You only need the inode for most of this. The exception is
fi->num_locks, so you may need to test for that in a different way.

> It crashed in Line#47 and the 'fl->fl_file' memory is:
> 
> crash> file.f_path.dentry,f_inode 0xffff952d4ebd8a00
>    f_path.dentry = 0x0
>    f_inode = 0x0,
> 
> Please NOTE: the 'filp' and 'fl->fl_file' are two different 'file struct'.
> 

Yep, I understand the bug. I just don't like the proposed fix. :)

> Can we fix this by using 'fl->fl_u' here ?
> 

Probably. You could take and hold an inode reference in there, and maybe
add a function that looks at whether there are any locks held against a
particular file, rather than trying to count locks in ceph_file_info.

> I was also thinking I could just call the 'get_file(file)' in 
> ceph_lock() and then in ceph_fl_release_lock() release the reference 
> counter. How about this ?
> 

That may work too, though again, I'd be worried about cyclical
dependencies, particularly with OFD locks. If the lock holds a reference
to the file, then can the file's refcount ever go to zero if the lock is
never explicitly released? I think not.

You may also need to consider flock locks too, since they have similar
ownership semantics to OFD locks.
-- 
Jeff Layton <jlayton@kernel.org>

Re: [RFC PATCH] fs/lock: increase the filp's reference for Posix-style locks

[Xiubo Li]

On 07/11/2022 20:29, Jeff Layton wrote:
> On Mon, 2022-11-07 at 20:03 +0800, Xiubo Li wrote:
>> On 07/11/2022 18:33, Jeff Layton wrote:
>>> On Mon, 2022-11-07 at 17:52 +0800, xiubli@redhat.com wrote:
[...]
>>>> diff --git a/io_uring/openclose.c b/io_uring/openclose.c
>>>> index 67178e4bb282..5a12cdf7f8d0 100644
>>>> --- a/io_uring/openclose.c
>>>> +++ b/io_uring/openclose.c
>>>> @@ -212,6 +212,7 @@ int io_close_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
>>>>    int io_close(struct io_kiocb *req, unsigned int issue_flags)
>>>>    {
>>>>    	struct files_struct *files = current->files;
>>>> +	fl_owner_t owner = file_lock_make_thread_owner(files);
>>>>    	struct io_close *close = io_kiocb_to_cmd(req, struct io_close);
>>>>    	struct fdtable *fdt;
>>>>    	struct file *file;
>>>> @@ -247,7 +248,7 @@ int io_close(struct io_kiocb *req, unsigned int issue_flags)
>>>>    		goto err;
>>>>    
>>>>    	/* No ->flush() or already async, safely close from here */
>>>> -	ret = filp_close(file, current->files);
>>>> +	ret = filp_close(file, owner);
>>>>    err:
>>>>    	if (ret < 0)
>>>>    		req_set_fail(req);
>>> I think this is the wrong approach to fixing this. It also looks like
>>> you could hit a similar problem with OFD locks and this patch wouldn't
>>> address that issue.
>> For the OFD locks they will set the 'file' struct as the owner just as
>> the flock does, it should be okay and I don't think it has this issue if
>> my understanding is correct here.
>>
> They set the the owner to "file", but they don't hold a reference to it.
> With OFD locks, the file is what holds references to the lock, not the
> reverse.

Yeah, right. But for both OFD and flock they shouldn't hit this issue, 
because it when removing all the locks having the same owner, which is 
the 'file', passed by filp_close(filp), the 'file' reference counter 
must be larger than 0. Because the filp_close() is still using it.

This is why using the thread id as the owner is a special case for 
Posix-style lock.

>
>>> The real bug seems to be that ceph_fl_release_lock dereferences fl_file,
>>> at a point when it shouldn't rely on that being valid. Most filesystems
>>> stash some info in fl->fl_u if they need to do bookkeeping after
>>> releasing a lock. Perhaps ceph should be doing something similar?
>> This is the 'filp' memory in filp_close(filp, ...):
>>
>> crash> file.f_path.dentry,f_inode 0xffff952d7ab46200
>>     f_path.dentry = 0xffff9521b121cb40
>>     f_inode = 0xffff951f3ea33550,
>>
>> We can see the 'f_inode' is pointing to the correct inode memory.
>>
>>
>>
>> While later in 'ceph_fl_release_lock()':
>>
>> 41 static void ceph_fl_release_lock(struct file_lock *fl)
>> 42 {
>> 43     struct ceph_file_info *fi = fl->fl_file->private_data;
>> 44     struct inode *inode = file_inode(fl->fl_file);
>> 45     struct ceph_inode_info *ci = ceph_inode(inode);
>> 46     atomic_dec(&fi->num_locks);
>> 47     if (atomic_dec_and_test(&ci->i_filelock_ref)) {
>> 48         /* clear error when all locks are released */
>> 49         spin_lock(&ci->i_ceph_lock);
>> 50         ci->i_ceph_flags &= ~CEPH_I_ERROR_FILELOCK;
>> 51         spin_unlock(&ci->i_ceph_lock);
>> 52     }
>> 53 }
>>
> You only need the inode for most of this. The exception is
> fi->num_locks, so you may need to test for that in a different way.
>
>> It crashed in Line#47 and the 'fl->fl_file' memory is:
>>
>> crash> file.f_path.dentry,f_inode 0xffff952d4ebd8a00
>>     f_path.dentry = 0x0
>>     f_inode = 0x0,
>>
>> Please NOTE: the 'filp' and 'fl->fl_file' are two different 'file struct'.
>>
> Yep, I understand the bug. I just don't like the proposed fix. :)

Yeah, I also think this approach is ugly :-)

>> Can we fix this by using 'fl->fl_u' here ?
>>
> Probably. You could take and hold an inode reference in there, and maybe
> add a function that looks at whether there are any locks held against a
> particular file, rather than trying to count locks in ceph_file_info.

Okay, this sounds good.

Let me try this tomorrow.

>> I was also thinking I could just call the 'get_file(file)' in
>> ceph_lock() and then in ceph_fl_release_lock() release the reference
>> counter. How about this ?
>>
> That may work too, though again, I'd be worried about cyclical
> dependencies, particularly with OFD locks. If the lock holds a reference
> to the file, then can the file's refcount ever go to zero if the lock is
> never explicitly released? I think not.
>
> You may also need to consider flock locks too, since they have similar
> ownership semantics to OFD locks.

I will send a V2 later.

Thanks Jeff!

- Xiubo