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* [PATCH 5.12] io_uring: Convert personality_idr to XArray
@ 2021-03-08 14:16 Pavel Begunkov
  2021-03-08 14:22 ` Pavel Begunkov
  2021-03-09 20:53 ` Jens Axboe
  0 siblings, 2 replies; 12+ messages in thread
From: Pavel Begunkov @ 2021-03-08 14:16 UTC (permalink / raw)
  To: Jens Axboe, io-uring
  Cc: Matthew Wilcox, yangerkun, asml.silence, Stefan Metzmacher

From: "Matthew Wilcox (Oracle)" <[email protected]>

You can't call idr_remove() from within a idr_for_each() callback,
but you can call xa_erase() from an xa_for_each() loop, so switch the
entire personality_idr from the IDR to the XArray.  This manifests as a
use-after-free as idr_for_each() attempts to walk the rest of the node
after removing the last entry from it.

Fixes: 071698e13ac6 ("io_uring: allow registering credentials")
Cc: [email protected] # 5.6+
Reported-by: yangerkun <[email protected]>
Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
[Pavel: rebased (creds load was moved into io_init_req())]
Signed-off-by: Pavel Begunkov <[email protected]>
---
 fs/io_uring.c | 47 ++++++++++++++++++++++++-----------------------
 1 file changed, 24 insertions(+), 23 deletions(-)

p.s. passes liburing tests well

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 5ef9f836cccc..5505e19f1391 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -407,7 +407,8 @@ struct io_ring_ctx {
 
 	struct idr		io_buffer_idr;
 
-	struct idr		personality_idr;
+	struct xarray		personalities;
+	u32			pers_next;
 
 	struct {
 		unsigned		cached_cq_tail;
@@ -1138,7 +1139,7 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 	init_completion(&ctx->ref_comp);
 	init_completion(&ctx->sq_thread_comp);
 	idr_init(&ctx->io_buffer_idr);
-	idr_init(&ctx->personality_idr);
+	xa_init_flags(&ctx->personalities, XA_FLAGS_ALLOC1);
 	mutex_init(&ctx->uring_lock);
 	init_waitqueue_head(&ctx->wait);
 	spin_lock_init(&ctx->completion_lock);
@@ -6338,7 +6339,7 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
 	req->work.list.next = NULL;
 	personality = READ_ONCE(sqe->personality);
 	if (personality) {
-		req->work.creds = idr_find(&ctx->personality_idr, personality);
+		req->work.creds = xa_load(&ctx->personalities, personality);
 		if (!req->work.creds)
 			return -EINVAL;
 		get_cred(req->work.creds);
@@ -8359,7 +8360,6 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
 	mutex_unlock(&ctx->uring_lock);
 	io_eventfd_unregister(ctx);
 	io_destroy_buffers(ctx);
-	idr_destroy(&ctx->personality_idr);
 
 #if defined(CONFIG_UNIX)
 	if (ctx->ring_sock) {
@@ -8424,7 +8424,7 @@ static int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id)
 {
 	const struct cred *creds;
 
-	creds = idr_remove(&ctx->personality_idr, id);
+	creds = xa_erase(&ctx->personalities, id);
 	if (creds) {
 		put_cred(creds);
 		return 0;
@@ -8433,14 +8433,6 @@ static int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id)
 	return -EINVAL;
 }
 
-static int io_remove_personalities(int id, void *p, void *data)
-{
-	struct io_ring_ctx *ctx = data;
-
-	io_unregister_personality(ctx, id);
-	return 0;
-}
-
 static bool io_run_ctx_fallback(struct io_ring_ctx *ctx)
 {
 	struct callback_head *work, *next;
@@ -8530,13 +8522,17 @@ static void io_ring_exit_work(struct work_struct *work)
 
 static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
 {
+	unsigned long index;
+	struct creds *creds;
+
 	mutex_lock(&ctx->uring_lock);
 	percpu_ref_kill(&ctx->refs);
 	/* if force is set, the ring is going away. always drop after that */
 	ctx->cq_overflow_flushed = 1;
 	if (ctx->rings)
 		__io_cqring_overflow_flush(ctx, true, NULL, NULL);
-	idr_for_each(&ctx->personality_idr, io_remove_personalities, ctx);
+	xa_for_each(&ctx->personalities, index, creds)
+		io_unregister_personality(ctx, index);
 	mutex_unlock(&ctx->uring_lock);
 
 	io_kill_timeouts(ctx, NULL, NULL);
@@ -9166,10 +9162,9 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 }
 
 #ifdef CONFIG_PROC_FS
-static int io_uring_show_cred(int id, void *p, void *data)
+static int io_uring_show_cred(struct seq_file *m, unsigned int id,
+		const struct cred *cred)
 {
-	const struct cred *cred = p;
-	struct seq_file *m = data;
 	struct user_namespace *uns = seq_user_ns(m);
 	struct group_info *gi;
 	kernel_cap_t cap;
@@ -9237,9 +9232,13 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
 		seq_printf(m, "%5u: 0x%llx/%u\n", i, buf->ubuf,
 						(unsigned int) buf->len);
 	}
-	if (has_lock && !idr_is_empty(&ctx->personality_idr)) {
+	if (has_lock && !xa_empty(&ctx->personalities)) {
+		unsigned long index;
+		const struct cred *cred;
+
 		seq_printf(m, "Personalities:\n");
-		idr_for_each(&ctx->personality_idr, io_uring_show_cred, m);
+		xa_for_each(&ctx->personalities, index, cred)
+			io_uring_show_cred(m, index, cred);
 	}
 	seq_printf(m, "PollList:\n");
 	spin_lock_irq(&ctx->completion_lock);
@@ -9568,14 +9567,16 @@ static int io_probe(struct io_ring_ctx *ctx, void __user *arg, unsigned nr_args)
 static int io_register_personality(struct io_ring_ctx *ctx)
 {
 	const struct cred *creds;
+	u32 id;
 	int ret;
 
 	creds = get_current_cred();
 
-	ret = idr_alloc_cyclic(&ctx->personality_idr, (void *) creds, 1,
-				USHRT_MAX, GFP_KERNEL);
-	if (ret < 0)
-		put_cred(creds);
+	ret = xa_alloc_cyclic(&ctx->personalities, &id, (void *)creds,
+			XA_LIMIT(0, USHRT_MAX), &ctx->pers_next, GFP_KERNEL);
+	if (!ret)
+		return id;
+	put_cred(creds);
 	return ret;
 }
 
-- 
2.24.0


^ permalink raw reply related	[flat|nested] 12+ messages in thread

end of thread, other threads:[~2021-03-13 20:23 UTC | newest]

Thread overview: 12+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2021-03-08 14:16 [PATCH 5.12] io_uring: Convert personality_idr to XArray Pavel Begunkov
2021-03-08 14:22 ` Pavel Begunkov
2021-03-08 16:16   ` Matthew Wilcox
2021-03-09 11:23   ` yangerkun
2021-03-13  8:02     ` yangerkun
2021-03-13 15:34       ` Jens Axboe
2021-03-13 19:01         ` Jens Axboe
2021-03-13 19:30           ` Jens Axboe
2021-03-13 19:54             ` Matthew Wilcox
2021-03-13 20:13               ` Jens Axboe
2021-03-13 20:22                 ` Jens Axboe
2021-03-09 20:53 ` Jens Axboe

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