[PATCH 0/2] fixes for syzbot reports

[PATCH 0/2] fixes for syzbot reports

[Pavel Begunkov]

2/2 is io_uring double free reported multiple times,
For 1/1 we may leak uring file references and miss
cancellations for the creator task.

Pavel Begunkov (2):
  io_uring: fix ignoring xa_store errors
  io_uring: fix double io_uring free

 fs/io_uring.c | 79 +++++++++++++++++++++++++++++----------------------
 1 file changed, 45 insertions(+), 34 deletions(-)

-- 
2.24.0

[PATCH 1/2] io_uring: fix ignoring xa_store errors

[Pavel Begunkov]

xa_store() may fail, check the result.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index fbf747803dbc..846c635d0620 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8852,10 +8852,9 @@ static void io_uring_cancel_task_requests(struct io_ring_ctx *ctx,
 static int io_uring_add_task_file(struct io_ring_ctx *ctx, struct file *file)
 {
 	struct io_uring_task *tctx = current->io_uring;
+	int ret;
 
 	if (unlikely(!tctx)) {
-		int ret;
-
 		ret = io_uring_alloc_task_context(current);
 		if (unlikely(ret))
 			return ret;
@@ -8866,7 +8865,12 @@ static int io_uring_add_task_file(struct io_ring_ctx *ctx, struct file *file)
 
 		if (!old) {
 			get_file(file);
-			xa_store(&tctx->xa, (unsigned long)file, file, GFP_KERNEL);
+			ret = xa_err(xa_store(&tctx->xa, (unsigned long)file,
+						file, GFP_KERNEL));
+			if (ret) {
+				fput(file);
+				return ret;
+			}
 		}
 		tctx->last = file;
 	}
-- 
2.24.0

Re: [PATCH 1/2] io_uring: fix ignoring xa_store errors

[Chaitanya Kulkarni]

On 12/21/20 10:40, Pavel Begunkov wrote:
> @@ -8866,7 +8865,12 @@ static int io_uring_add_task_file(struct io_ring_ctx *ctx, struct file *file)
>  
>  		if (!old) {
>  			get_file(file);
> -			xa_store(&tctx->xa, (unsigned long)file, file, GFP_KERNEL);
> +			ret = xa_err(xa_store(&tctx->xa, (unsigned long)file,
> +						file, GFP_KERNEL));
> +			if (ret) {
> +				fput(file);
> +				return ret;
> +			}
>  		}
>  		tctx->last = file;
>  	}
Looks good.

Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>

[PATCH 2/2] io_uring: fix double io_uring free

[Pavel Begunkov]

Once we created a file for current context during setup, we should not
call io_ring_ctx_wait_and_kill() directly as it'll be done by fput(file)

Reported-by: syzbot+c9937dfb2303a5f18640@syzkaller.appspotmail.com
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 69 ++++++++++++++++++++++++++++-----------------------
 1 file changed, 38 insertions(+), 31 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 846c635d0620..19ec1898b934 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9379,55 +9379,52 @@ static int io_allocate_scq_urings(struct io_ring_ctx *ctx,
 	return 0;
 }
 
+static int io_uring_install_fd(struct io_ring_ctx *ctx, struct file *file)
+{
+	int ret, fd;
+
+	fd = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
+	if (fd < 0)
+		return fd;
+
+	ret = io_uring_add_task_file(ctx, file);
+	if (ret) {
+		put_unused_fd(fd);
+		return ret;
+	}
+	fd_install(fd, file);
+	return fd;
+}
+
 /*
  * Allocate an anonymous fd, this is what constitutes the application
  * visible backing of an io_uring instance. The application mmaps this
  * fd to gain access to the SQ/CQ ring details. If UNIX sockets are enabled,
  * we have to tie this fd to a socket for file garbage collection purposes.
  */
-static int io_uring_get_fd(struct io_ring_ctx *ctx)
+static struct file *io_uring_get_file(struct io_ring_ctx *ctx)
 {
 	struct file *file;
 	int ret;
-	int fd;
 
 #if defined(CONFIG_UNIX)
 	ret = sock_create_kern(&init_net, PF_UNIX, SOCK_RAW, IPPROTO_IP,
 				&ctx->ring_sock);
 	if (ret)
-		return ret;
+		return ERR_PTR(ret);
 #endif
 
-	ret = get_unused_fd_flags(O_RDWR | O_CLOEXEC);
-	if (ret < 0)
-		goto err;
-	fd = ret;
-
 	file = anon_inode_getfile("[io_uring]", &io_uring_fops, ctx,
 					O_RDWR | O_CLOEXEC);
-	if (IS_ERR(file)) {
-		put_unused_fd(fd);
-		ret = PTR_ERR(file);
-		goto err;
-	}
-
 #if defined(CONFIG_UNIX)
-	ctx->ring_sock->file = file;
-#endif
-	ret = io_uring_add_task_file(ctx, file);
-	if (ret) {
-		fput(file);
-		put_unused_fd(fd);
-		goto err;
+	if (IS_ERR(file)) {
+		sock_release(ctx->ring_sock);
+		ctx->ring_sock = NULL;
+	} else {
+		ctx->ring_sock->file = file;
 	}
-	fd_install(fd, file);
-	return fd;
-err:
-#if defined(CONFIG_UNIX)
-	sock_release(ctx->ring_sock);
-	ctx->ring_sock = NULL;
 #endif
-	return ret;
+	return file;
 }
 
 static int io_uring_create(unsigned entries, struct io_uring_params *p,
@@ -9435,6 +9432,7 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p,
 {
 	struct user_struct *user = NULL;
 	struct io_ring_ctx *ctx;
+	struct file *file;
 	bool limit_mem;
 	int ret;
 
@@ -9582,13 +9580,22 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p,
 		goto err;
 	}
 
+	file = io_uring_get_file(ctx);
+	if (IS_ERR(file)) {
+		ret = PTR_ERR(file);
+		goto err;
+	}
+
 	/*
 	 * Install ring fd as the very last thing, so we don't risk someone
 	 * having closed it before we finish setup
 	 */
-	ret = io_uring_get_fd(ctx);
-	if (ret < 0)
-		goto err;
+	ret = io_uring_install_fd(ctx, file);
+	if (ret < 0) {
+		/* fput will clean it up */
+		fput(file);
+		return ret;
+	}
 
 	trace_io_uring_create(ret, ctx, p->sq_entries, p->cq_entries, p->flags);
 	return ret;
-- 
2.24.0