[PATCH] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

[PATCH] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

[Peilin Ye]

From: Peilin Ye <peilin.ye@bytedance.com>

Currently @audit_context is allocated twice for io_uring workers:

  1. copy_process() calls audit_alloc();
  2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
     is effectively audit_alloc()) and overwrites @audit_context,
     causing:

  BUG: memory leak
  unreferenced object 0xffff888144547400 (size 1024):
<...>
    hex dump (first 32 bytes):
      00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    backtrace:
      [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
      [<ffffffff81239e63>] copy_process+0xcd3/0x2340
      [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
      [<ffffffff81686604>] create_io_worker+0xb4/0x230
      [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
      [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
      [<ffffffff816768b3>] io_queue_async+0x113/0x180
      [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
      [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
      [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
      [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
      [<ffffffff8125a688>] get_signal+0xc18/0xf10
      [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
      [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
      [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
      [<ffffffff844a7e80>] do_syscall_64+0x40/0x80

Then,

  3. io_sq_thread() or io_wqe_worker() frees @audit_context using
     audit_free();
  4. do_exit() eventually calls audit_free() again, which is okay
     because audit_free() does a NULL check.

Free the old @audit_context first in audit_alloc_kernel(), and delete
the redundant calls to audit_free() for less confusion.

Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
Cc: stable@vger.kernel.org
Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
---
Hi all,

A better way to fix this memleak would probably be checking
@args->io_thread in copy_process()?  Something like:

    if (args->io_thread)
	retval = audit_alloc_kernel();
    else
	retval = audit_alloc();

But I didn't want to add another if to copy_process() for this bugfix.
Please suggest, thanks!

Peilin Ye

 fs/io-wq.c       | 1 -
 fs/io_uring.c    | 2 --
 kernel/auditsc.c | 1 +
 3 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 824623bcf1a5..0f4804a5e873 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -670,7 +670,6 @@ static int io_wqe_worker(void *data)
 	if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
 		io_worker_handle_work(worker);
 
-	audit_free(current);
 	io_worker_exit(worker);
 	return 0;
 }
diff --git a/fs/io_uring.c b/fs/io_uring.c
index e8e769be9ed0..0f27914f37f2 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9283,8 +9283,6 @@ static int io_sq_thread(void *data)
 	io_run_task_work();
 	mutex_unlock(&sqd->lock);
 
-	audit_free(current);
-
 	complete(&sqd->exited);
 	do_exit(0);
 }
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 3a8c9d744800..7948090fd12f 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1095,6 +1095,7 @@ int audit_alloc_kernel(struct task_struct *tsk)
 	 * 2. The {set,clear}_task_syscall_work() ops likely have zero effect
 	 * on these internal kernel tasks, but they probably don't hurt either.
 	 */
+	__audit_free(current);
 	return audit_alloc(tsk);
 }
 
-- 
2.20.1

Re: [PATCH] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

[Paul Moore]

On Wed, Aug 3, 2022 at 1:03 AM Peilin Ye <yepeilin.cs@gmail.com> wrote:
>
> From: Peilin Ye <peilin.ye@bytedance.com>
>
> Currently @audit_context is allocated twice for io_uring workers:
>
>   1. copy_process() calls audit_alloc();
>   2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
>      is effectively audit_alloc()) and overwrites @audit_context,
>      causing:
>
>   BUG: memory leak
>   unreferenced object 0xffff888144547400 (size 1024):
> <...>
>     hex dump (first 32 bytes):
>       00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
>       00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     backtrace:
>       [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
>       [<ffffffff81239e63>] copy_process+0xcd3/0x2340
>       [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
>       [<ffffffff81686604>] create_io_worker+0xb4/0x230
>       [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
>       [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
>       [<ffffffff816768b3>] io_queue_async+0x113/0x180
>       [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
>       [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
>       [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
>       [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
>       [<ffffffff8125a688>] get_signal+0xc18/0xf10
>       [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
>       [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
>       [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
>       [<ffffffff844a7e80>] do_syscall_64+0x40/0x80
>
> Then,
>
>   3. io_sq_thread() or io_wqe_worker() frees @audit_context using
>      audit_free();
>   4. do_exit() eventually calls audit_free() again, which is okay
>      because audit_free() does a NULL check.
>
> Free the old @audit_context first in audit_alloc_kernel(), and delete
> the redundant calls to audit_free() for less confusion.
>
> Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
> Cc: stable@vger.kernel.org
> Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
> ---
> Hi all,
>
> A better way to fix this memleak would probably be checking
> @args->io_thread in copy_process()?  Something like:
>
>     if (args->io_thread)
>         retval = audit_alloc_kernel();
>     else
>         retval = audit_alloc();
>
> But I didn't want to add another if to copy_process() for this bugfix.
> Please suggest, thanks!

Thanks for the report and patch!  I'll take a closer look at this
today and get back to you.

>  fs/io-wq.c       | 1 -
>  fs/io_uring.c    | 2 --
>  kernel/auditsc.c | 1 +
>  3 files changed, 1 insertion(+), 3 deletions(-)

-- 
paul-moore.com

Re: [PATCH] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

[Paul Moore]

On Wed, Aug 3, 2022 at 9:16 AM Paul Moore <paul@paul-moore.com> wrote:
> On Wed, Aug 3, 2022 at 1:03 AM Peilin Ye <yepeilin.cs@gmail.com> wrote:
> >
> > Currently @audit_context is allocated twice for io_uring workers:
> >
> >   1. copy_process() calls audit_alloc();
> >   2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
> >      is effectively audit_alloc()) and overwrites @audit_context,
> >      causing:
> >
> >   BUG: memory leak
> >   unreferenced object 0xffff888144547400 (size 1024):
> > <...>
> >     hex dump (first 32 bytes):
> >       00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
> >       00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> >     backtrace:
> >       [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
> >       [<ffffffff81239e63>] copy_process+0xcd3/0x2340
> >       [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
> >       [<ffffffff81686604>] create_io_worker+0xb4/0x230
> >       [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
> >       [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
> >       [<ffffffff816768b3>] io_queue_async+0x113/0x180
> >       [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
> >       [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
> >       [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
> >       [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
> >       [<ffffffff8125a688>] get_signal+0xc18/0xf10
> >       [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
> >       [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
> >       [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
> >       [<ffffffff844a7e80>] do_syscall_64+0x40/0x80
> >
> > Then,
> >
> >   3. io_sq_thread() or io_wqe_worker() frees @audit_context using
> >      audit_free();
> >   4. do_exit() eventually calls audit_free() again, which is okay
> >      because audit_free() does a NULL check.
> >
> > Free the old @audit_context first in audit_alloc_kernel(), and delete
> > the redundant calls to audit_free() for less confusion.
> >
> > Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
> > ---
> > Hi all,
> >
> > A better way to fix this memleak would probably be checking
> > @args->io_thread in copy_process()?  Something like:
> >
> >     if (args->io_thread)
> >         retval = audit_alloc_kernel();
> >     else
> >         retval = audit_alloc();
> >
> > But I didn't want to add another if to copy_process() for this bugfix.
> > Please suggest, thanks!
>
> Thanks for the report and patch!  I'll take a closer look at this
> today and get back to you.

I think the best solution to this is simply to remove the calls to
audit_alloc_kernel() in the io_uring and io-wq code, as well as the
audit_alloc_kernel() function itself.  As long as create_io_thread()
ends up calling copy_process to create the new kernel thread the
audit_context should be allocated correctly.  Peilin Ye, are you able
to draft a patch to do that and give it a test?

For those that may be wondering how this happened (I definitely was!),
it looks like when I first started working on the LSM/audit support
for io_uring it was before the v5.12-rc1 release when
create_io_thread() was introduced.  Prior to create_io_thread() it
appears that io_uring/io-wq wasn't calling into copy_process() and
thus was not getting an audit_context allocated in the kernel thread's
task_struct; the solution for those original development drafts was to
add a call to a new audit_alloc_kernel() which would handle the
audit_context allocation.  Unfortunately, I didn't notice the move to
create_io_thread() during development and the redundant
audit_alloc_kernel() calls remained :/

-- 
paul-moore.com

Re: [PATCH] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

[Jens Axboe]

On 8/3/22 1:28 PM, Paul Moore wrote:
> On Wed, Aug 3, 2022 at 9:16 AM Paul Moore <paul@paul-moore.com> wrote:
>> On Wed, Aug 3, 2022 at 1:03 AM Peilin Ye <yepeilin.cs@gmail.com> wrote:
>>>
>>> Currently @audit_context is allocated twice for io_uring workers:
>>>
>>>   1. copy_process() calls audit_alloc();
>>>   2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
>>>      is effectively audit_alloc()) and overwrites @audit_context,
>>>      causing:
>>>
>>>   BUG: memory leak
>>>   unreferenced object 0xffff888144547400 (size 1024):
>>> <...>
>>>     hex dump (first 32 bytes):
>>>       00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
>>>       00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>>     backtrace:
>>>       [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
>>>       [<ffffffff81239e63>] copy_process+0xcd3/0x2340
>>>       [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
>>>       [<ffffffff81686604>] create_io_worker+0xb4/0x230
>>>       [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
>>>       [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
>>>       [<ffffffff816768b3>] io_queue_async+0x113/0x180
>>>       [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
>>>       [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
>>>       [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
>>>       [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
>>>       [<ffffffff8125a688>] get_signal+0xc18/0xf10
>>>       [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
>>>       [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
>>>       [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
>>>       [<ffffffff844a7e80>] do_syscall_64+0x40/0x80
>>>
>>> Then,
>>>
>>>   3. io_sq_thread() or io_wqe_worker() frees @audit_context using
>>>      audit_free();
>>>   4. do_exit() eventually calls audit_free() again, which is okay
>>>      because audit_free() does a NULL check.
>>>
>>> Free the old @audit_context first in audit_alloc_kernel(), and delete
>>> the redundant calls to audit_free() for less confusion.
>>>
>>> Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
>>> Cc: stable@vger.kernel.org
>>> Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
>>> ---
>>> Hi all,
>>>
>>> A better way to fix this memleak would probably be checking
>>> @args->io_thread in copy_process()?  Something like:
>>>
>>>     if (args->io_thread)
>>>         retval = audit_alloc_kernel();
>>>     else
>>>         retval = audit_alloc();
>>>
>>> But I didn't want to add another if to copy_process() for this bugfix.
>>> Please suggest, thanks!
>>
>> Thanks for the report and patch!  I'll take a closer look at this
>> today and get back to you.
> 
> I think the best solution to this is simply to remove the calls to
> audit_alloc_kernel() in the io_uring and io-wq code, as well as the
> audit_alloc_kernel() function itself.  As long as create_io_thread()
> ends up calling copy_process to create the new kernel thread the
> audit_context should be allocated correctly.  Peilin Ye, are you able
> to draft a patch to do that and give it a test?
> 
> For those that may be wondering how this happened (I definitely was!),
> it looks like when I first started working on the LSM/audit support
> for io_uring it was before the v5.12-rc1 release when
> create_io_thread() was introduced.  Prior to create_io_thread() it
> appears that io_uring/io-wq wasn't calling into copy_process() and
> thus was not getting an audit_context allocated in the kernel thread's
> task_struct; the solution for those original development drafts was to
> add a call to a new audit_alloc_kernel() which would handle the
> audit_context allocation.  Unfortunately, I didn't notice the move to
> create_io_thread() during development and the redundant
> audit_alloc_kernel() calls remained :/

I agree with your analysis and suggested solution. Post the native io-wq
workers create_io_thread() -> copy_process() is always used for io-wq
(and sqpoll, for that matter).

-- 
Jens Axboe

Re: [PATCH] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

[Peilin Ye]

Hi,

On Wed, Aug 03, 2022 at 03:28:19PM -0400, Paul Moore wrote:
> On Wed, Aug 3, 2022 at 9:16 AM Paul Moore <paul@paul-moore.com> wrote:
> > On Wed, Aug 3, 2022 at 1:03 AM Peilin Ye <yepeilin.cs@gmail.com> wrote:
> > > Hi all,
> > >
> > > A better way to fix this memleak would probably be checking
> > > @args->io_thread in copy_process()?  Something like:
> > >
> > >     if (args->io_thread)
> > >         retval = audit_alloc_kernel();
> > >     else
> > >         retval = audit_alloc();
> > >
> > > But I didn't want to add another if to copy_process() for this bugfix.
> > > Please suggest, thanks!
> >
> > Thanks for the report and patch!  I'll take a closer look at this
> > today and get back to you.
> 
> I think the best solution to this is simply to remove the calls to
> audit_alloc_kernel() in the io_uring and io-wq code, as well as the
> audit_alloc_kernel() function itself.  As long as create_io_thread()
> ends up calling copy_process to create the new kernel thread the
> audit_context should be allocated correctly.  Peilin Ye, are you able
> to draft a patch to do that and give it a test?

Sure, I will write a v2 today.  Thanks for the suggestion!

> For those that may be wondering how this happened (I definitely was!),
> it looks like when I first started working on the LSM/audit support
> for io_uring it was before the v5.12-rc1 release when
> create_io_thread() was introduced.  Prior to create_io_thread() it
> appears that io_uring/io-wq wasn't calling into copy_process() and
> thus was not getting an audit_context allocated in the kernel thread's
> task_struct; the solution for those original development drafts was to
> add a call to a new audit_alloc_kernel() which would handle the
> audit_context allocation.  Unfortunately, I didn't notice the move to
> create_io_thread() during development and the redundant
> audit_alloc_kernel() calls remained :/

Thanks,
Peilin Ye

[PATCH v2] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

[Peilin Ye]

From: Peilin Ye <peilin.ye@bytedance.com>

Currently @audit_context is allocated twice for io_uring workers:

  1. copy_process() calls audit_alloc();
  2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
     is effectively audit_alloc()) and overwrites @audit_context,
     causing:

  BUG: memory leak
  unreferenced object 0xffff888144547400 (size 1024):
<...>
    hex dump (first 32 bytes):
      00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    backtrace:
      [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
      [<ffffffff81239e63>] copy_process+0xcd3/0x2340
      [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
      [<ffffffff81686604>] create_io_worker+0xb4/0x230
      [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
      [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
      [<ffffffff816768b3>] io_queue_async+0x113/0x180
      [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
      [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
      [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
      [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
      [<ffffffff8125a688>] get_signal+0xc18/0xf10
      [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
      [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
      [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
      [<ffffffff844a7e80>] do_syscall_64+0x40/0x80

Then,

  3. io_sq_thread() or io_wqe_worker() frees @audit_context using
     audit_free();
  4. do_exit() eventually calls audit_free() again, which is okay
     because audit_free() does a NULL check.

As suggested by Paul Moore, fix it by deleting audit_alloc_kernel() and
redundant audit_free() calls.

Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
Suggested-by: Paul Moore <paul@paul-moore.com>
Cc: stable@vger.kernel.org
Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
---
Change since v1:
  - Delete audit_alloc_kernel() (Paul Moore)

 fs/io-wq.c            |  3 ---
 fs/io_uring.c         |  4 ----
 include/linux/audit.h |  5 -----
 kernel/auditsc.c      | 25 -------------------------
 4 files changed, 37 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 824623bcf1a5..4d8a77a2a150 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -634,8 +634,6 @@ static int io_wqe_worker(void *data)
 	snprintf(buf, sizeof(buf), "iou-wrk-%d", wq->task->pid);
 	set_task_comm(current, buf);
 
-	audit_alloc_kernel(current);
-
 	while (!test_bit(IO_WQ_BIT_EXIT, &wq->state)) {
 		long ret;
 
@@ -670,7 +668,6 @@ static int io_wqe_worker(void *data)
 	if (test_bit(IO_WQ_BIT_EXIT, &wq->state))
 		io_worker_handle_work(worker);
 
-	audit_free(current);
 	io_worker_exit(worker);
 	return 0;
 }
diff --git a/fs/io_uring.c b/fs/io_uring.c
index e8e769be9ed0..e0da0d2f71f2 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9208,8 +9208,6 @@ static int io_sq_thread(void *data)
 		set_cpus_allowed_ptr(current, cpu_online_mask);
 	current->flags |= PF_NO_SETAFFINITY;
 
-	audit_alloc_kernel(current);
-
 	mutex_lock(&sqd->lock);
 	while (1) {
 		bool cap_entries, sqt_spin = false;
@@ -9283,8 +9281,6 @@ static int io_sq_thread(void *data)
 	io_run_task_work();
 	mutex_unlock(&sqd->lock);
 
-	audit_free(current);
-
 	complete(&sqd->exited);
 	do_exit(0);
 }
diff --git a/include/linux/audit.h b/include/linux/audit.h
index cece70231138..c313df466e6e 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -287,7 +287,6 @@ static inline int audit_signal_info(int sig, struct task_struct *t)
 /* These are defined in auditsc.c */
 				/* Public API */
 extern int  audit_alloc(struct task_struct *task);
-extern int  audit_alloc_kernel(struct task_struct *task);
 extern void __audit_free(struct task_struct *task);
 extern void __audit_uring_entry(u8 op);
 extern void __audit_uring_exit(int success, long code);
@@ -580,10 +579,6 @@ static inline int audit_alloc(struct task_struct *task)
 {
 	return 0;
 }
-static inline int audit_alloc_kernel(struct task_struct *task)
-{
-	return 0;
-}
 static inline void audit_free(struct task_struct *task)
 { }
 static inline void audit_uring_entry(u8 op)
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 3a8c9d744800..dd8d9ab747c3 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -1073,31 +1073,6 @@ int audit_alloc(struct task_struct *tsk)
 	return 0;
 }
 
-/**
- * audit_alloc_kernel - allocate an audit_context for a kernel task
- * @tsk: the kernel task
- *
- * Similar to the audit_alloc() function, but intended for kernel private
- * threads.  Returns zero on success, negative values on failure.
- */
-int audit_alloc_kernel(struct task_struct *tsk)
-{
-	/*
-	 * At the moment we are just going to call into audit_alloc() to
-	 * simplify the code, but there two things to keep in mind with this
-	 * approach:
-	 *
-	 * 1. Filtering internal kernel tasks is a bit laughable in almost all
-	 * cases, but there is at least one case where there is a benefit:
-	 * the '-a task,never' case allows the admin to effectively disable
-	 * task auditing at runtime.
-	 *
-	 * 2. The {set,clear}_task_syscall_work() ops likely have zero effect
-	 * on these internal kernel tasks, but they probably don't hurt either.
-	 */
-	return audit_alloc(tsk);
-}
-
 static inline void audit_free_context(struct audit_context *context)
 {
 	/* resetting is extra work, but it is likely just noise */
-- 
2.20.1

Re: [PATCH v2] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

[Paul Moore]

On Wed, Aug 3, 2022 at 6:24 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
>
> From: Peilin Ye <peilin.ye@bytedance.com>
>
> Currently @audit_context is allocated twice for io_uring workers:
>
>   1. copy_process() calls audit_alloc();
>   2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
>      is effectively audit_alloc()) and overwrites @audit_context,
>      causing:
>
>   BUG: memory leak
>   unreferenced object 0xffff888144547400 (size 1024):
> <...>
>     hex dump (first 32 bytes):
>       00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
>       00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     backtrace:
>       [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
>       [<ffffffff81239e63>] copy_process+0xcd3/0x2340
>       [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
>       [<ffffffff81686604>] create_io_worker+0xb4/0x230
>       [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
>       [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
>       [<ffffffff816768b3>] io_queue_async+0x113/0x180
>       [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
>       [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
>       [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
>       [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
>       [<ffffffff8125a688>] get_signal+0xc18/0xf10
>       [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
>       [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
>       [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
>       [<ffffffff844a7e80>] do_syscall_64+0x40/0x80
>
> Then,
>
>   3. io_sq_thread() or io_wqe_worker() frees @audit_context using
>      audit_free();
>   4. do_exit() eventually calls audit_free() again, which is okay
>      because audit_free() does a NULL check.
>
> As suggested by Paul Moore, fix it by deleting audit_alloc_kernel() and
> redundant audit_free() calls.
>
> Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
> Suggested-by: Paul Moore <paul@paul-moore.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
> ---
> Change since v1:
>   - Delete audit_alloc_kernel() (Paul Moore)
>
>  fs/io-wq.c            |  3 ---
>  fs/io_uring.c         |  4 ----
>  include/linux/audit.h |  5 -----
>  kernel/auditsc.c      | 25 -------------------------
>  4 files changed, 37 deletions(-)

This looks good to me, thanks!  Although it looks like the io_uring
related changes will need to be applied by hand as they are pointing
to the old layout under fs/ as opposed to the newer layout in
io_uring/ introduced during this merge window.

Jens, did you want to take this via the io_uring tree or should I take
it via the audit tree?  If the latter, an ACK would be appreciated, if
the former my ACK is below.

Acked-by: Paul Moore <paul@paul-moore.com>

-- 
paul-moore.com

Re: [PATCH v2] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

[Jens Axboe]

On 8/4/22 7:51 AM, Paul Moore wrote:
> On Wed, Aug 3, 2022 at 6:24 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
>>
>> From: Peilin Ye <peilin.ye@bytedance.com>
>>
>> Currently @audit_context is allocated twice for io_uring workers:
>>
>>   1. copy_process() calls audit_alloc();
>>   2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
>>      is effectively audit_alloc()) and overwrites @audit_context,
>>      causing:
>>
>>   BUG: memory leak
>>   unreferenced object 0xffff888144547400 (size 1024):
>> <...>
>>     hex dump (first 32 bytes):
>>       00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
>>       00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>>     backtrace:
>>       [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
>>       [<ffffffff81239e63>] copy_process+0xcd3/0x2340
>>       [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
>>       [<ffffffff81686604>] create_io_worker+0xb4/0x230
>>       [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
>>       [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
>>       [<ffffffff816768b3>] io_queue_async+0x113/0x180
>>       [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
>>       [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
>>       [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
>>       [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
>>       [<ffffffff8125a688>] get_signal+0xc18/0xf10
>>       [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
>>       [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
>>       [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
>>       [<ffffffff844a7e80>] do_syscall_64+0x40/0x80
>>
>> Then,
>>
>>   3. io_sq_thread() or io_wqe_worker() frees @audit_context using
>>      audit_free();
>>   4. do_exit() eventually calls audit_free() again, which is okay
>>      because audit_free() does a NULL check.
>>
>> As suggested by Paul Moore, fix it by deleting audit_alloc_kernel() and
>> redundant audit_free() calls.
>>
>> Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
>> Suggested-by: Paul Moore <paul@paul-moore.com>
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
>> ---
>> Change since v1:
>>   - Delete audit_alloc_kernel() (Paul Moore)
>>
>>  fs/io-wq.c            |  3 ---
>>  fs/io_uring.c         |  4 ----
>>  include/linux/audit.h |  5 -----
>>  kernel/auditsc.c      | 25 -------------------------
>>  4 files changed, 37 deletions(-)
> 
> This looks good to me, thanks!  Although it looks like the io_uring
> related changes will need to be applied by hand as they are pointing
> to the old layout under fs/ as opposed to the newer layout in
> io_uring/ introduced during this merge window.
> 
> Jens, did you want to take this via the io_uring tree or should I take
> it via the audit tree?  If the latter, an ACK would be appreciated, if
> the former my ACK is below.
> 
> Acked-by: Paul Moore <paul@paul-moore.com>

Probably better if I take it, since I need to massage it into the
current tree anyway. We can then use this one as the base for the stable
backports that are going to be required.

-- 
Jens Axboe

Re: [PATCH v2] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

[Paul Moore]

On Thu, Aug 4, 2022 at 10:32 AM Jens Axboe <axboe@kernel.dk> wrote:
> On 8/4/22 7:51 AM, Paul Moore wrote:
> > On Wed, Aug 3, 2022 at 6:24 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
> >>
> >> From: Peilin Ye <peilin.ye@bytedance.com>
> >>
> >> Currently @audit_context is allocated twice for io_uring workers:
> >>
> >>   1. copy_process() calls audit_alloc();
> >>   2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
> >>      is effectively audit_alloc()) and overwrites @audit_context,
> >>      causing:
> >>
> >>   BUG: memory leak
> >>   unreferenced object 0xffff888144547400 (size 1024):
> >> <...>
> >>     hex dump (first 32 bytes):
> >>       00 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00  ................
> >>       00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> >>     backtrace:
> >>       [<ffffffff8135cfc3>] audit_alloc+0x133/0x210
> >>       [<ffffffff81239e63>] copy_process+0xcd3/0x2340
> >>       [<ffffffff8123b5f3>] create_io_thread+0x63/0x90
> >>       [<ffffffff81686604>] create_io_worker+0xb4/0x230
> >>       [<ffffffff81686f68>] io_wqe_enqueue+0x248/0x3b0
> >>       [<ffffffff8167663a>] io_queue_iowq+0xba/0x200
> >>       [<ffffffff816768b3>] io_queue_async+0x113/0x180
> >>       [<ffffffff816840df>] io_req_task_submit+0x18f/0x1a0
> >>       [<ffffffff816841cd>] io_apoll_task_func+0xdd/0x120
> >>       [<ffffffff8167d49f>] tctx_task_work+0x11f/0x570
> >>       [<ffffffff81272c4e>] task_work_run+0x7e/0xc0
> >>       [<ffffffff8125a688>] get_signal+0xc18/0xf10
> >>       [<ffffffff8111645b>] arch_do_signal_or_restart+0x2b/0x730
> >>       [<ffffffff812ea44e>] exit_to_user_mode_prepare+0x5e/0x180
> >>       [<ffffffff844ae1b2>] syscall_exit_to_user_mode+0x12/0x20
> >>       [<ffffffff844a7e80>] do_syscall_64+0x40/0x80
> >>
> >> Then,
> >>
> >>   3. io_sq_thread() or io_wqe_worker() frees @audit_context using
> >>      audit_free();
> >>   4. do_exit() eventually calls audit_free() again, which is okay
> >>      because audit_free() does a NULL check.
> >>
> >> As suggested by Paul Moore, fix it by deleting audit_alloc_kernel() and
> >> redundant audit_free() calls.
> >>
> >> Fixes: 5bd2182d58e9 ("audit,io_uring,io-wq: add some basic audit support to io_uring")
> >> Suggested-by: Paul Moore <paul@paul-moore.com>
> >> Cc: stable@vger.kernel.org
> >> Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
> >> ---
> >> Change since v1:
> >>   - Delete audit_alloc_kernel() (Paul Moore)
> >>
> >>  fs/io-wq.c            |  3 ---
> >>  fs/io_uring.c         |  4 ----
> >>  include/linux/audit.h |  5 -----
> >>  kernel/auditsc.c      | 25 -------------------------
> >>  4 files changed, 37 deletions(-)
> >
> > This looks good to me, thanks!  Although it looks like the io_uring
> > related changes will need to be applied by hand as they are pointing
> > to the old layout under fs/ as opposed to the newer layout in
> > io_uring/ introduced during this merge window.
> >
> > Jens, did you want to take this via the io_uring tree or should I take
> > it via the audit tree?  If the latter, an ACK would be appreciated, if
> > the former my ACK is below.
> >
> > Acked-by: Paul Moore <paul@paul-moore.com>
>
> Probably better if I take it, since I need to massage it into the
> current tree anyway. We can then use this one as the base for the stable
> backports that are going to be required.

Sounds good to me, thanks everyone.

-- 
paul-moore.com

Re: [PATCH v2] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()

[Jens Axboe]

On Wed, 3 Aug 2022 15:23:43 -0700, Peilin Ye wrote:
> From: Peilin Ye <peilin.ye@bytedance.com>
> 
> Currently @audit_context is allocated twice for io_uring workers:
> 
>   1. copy_process() calls audit_alloc();
>   2. io_sq_thread() or io_wqe_worker() calls audit_alloc_kernel() (which
>      is effectively audit_alloc()) and overwrites @audit_context,
>      causing:
> 
> [...]

Applied, thanks!

[1/1] audit, io_uring, io-wq: Fix memory leak in io_sq_thread() and io_wqe_worker()
      commit: f482aa98652795846cc55da98ebe331eb74f3d0b

Best regards,
-- 
Jens Axboe