[PATCH v5 3/6] io_uring: ensure io_uring_create() initializes submitter_task

[Caleb Sander Mateos <csander@purestorage.com>]

If io_uring_create() fails after allocating the struct io_ring_ctx, it
may call io_ring_ctx_wait_and_kill() before submitter_task has been
assigned. This is currently harmless, as the submit and register paths
that check submitter_task aren't reachable until the io_ring_ctx has
been successfully created. However, a subsequent commit will expect
submitter_task to be set for every IORING_SETUP_SINGLE_ISSUER &&
!IORING_SETUP_R_DISABLED ctx. So assign ctx->submitter_task prior to any
call to io_ring_ctx_wait_and_kill() in io_uring_create().

Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202512101405.a7a2bdb2-lkp@intel.com
Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
---
 io_uring/io_uring.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 44ff5756b328..6d6fe5bdebda 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -3647,10 +3647,19 @@ static __cold int io_uring_create(struct io_ctx_config *config)
 	 * memory (locked/pinned vm). It's not used for anything else.
 	 */
 	mmgrab(current->mm);
 	ctx->mm_account = current->mm;
 
+	if (ctx->flags & IORING_SETUP_SINGLE_ISSUER
+	    && !(ctx->flags & IORING_SETUP_R_DISABLED)) {
+		/*
+		 * Unlike io_register_enable_rings(), don't need WRITE_ONCE()
+		 * since ctx isn't yet accessible from other tasks
+		 */
+		ctx->submitter_task = get_task_struct(current);
+	}
+
 	ret = io_allocate_scq_urings(ctx, config);
 	if (ret)
 		goto err;
 
 	ret = io_sq_offload_create(ctx, p);
@@ -3662,19 +3671,10 @@ static __cold int io_uring_create(struct io_ctx_config *config)
 	if (copy_to_user(config->uptr, p, sizeof(*p))) {
 		ret = -EFAULT;
 		goto err;
 	}
 
-	if (ctx->flags & IORING_SETUP_SINGLE_ISSUER
-	    && !(ctx->flags & IORING_SETUP_R_DISABLED)) {
-		/*
-		 * Unlike io_register_enable_rings(), don't need WRITE_ONCE()
-		 * since ctx isn't yet accessible from other tasks
-		 */
-		ctx->submitter_task = get_task_struct(current);
-	}
-
 	file = io_uring_get_file(ctx);
 	if (IS_ERR(file)) {
 		ret = PTR_ERR(file);
 		goto err;
 	}
-- 
2.45.2