io_uring/msg_ring: reuse ctx->submitter_task read using READ_ONCE instead of re-reading it

[PATCH] io_uring/msg_ring: reuse ctx->submitter_task read using READ_ONCE instead of re-reading it

Posted by linke li 1 week, 4 days ago

In io_msg_exec_remote(), ctx->submitter_task is read using READ_ONCE at
the beginning of the function, checked, and then re-read from
ctx->submitter_task, voiding all guarantees of the checks. Reuse the value
that was read by READ_ONCE to ensure the consistency of the task struct
throughout the function.

Signed-off-by: linke li <lilinke99@qq.com>
---
 io_uring/msg_ring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/io_uring/msg_ring.c b/io_uring/msg_ring.c
index cd6dcf634ba3..d74670b39ed6 100644
--- a/io_uring/msg_ring.c
+++ b/io_uring/msg_ring.c
@@ -83,7 +83,7 @@ static int io_msg_exec_remote(struct io_kiocb *req, task_work_func_t func)
 		return -EOWNERDEAD;
 
 	init_task_work(&msg->tw, func);
-	if (task_work_add(ctx->submitter_task, &msg->tw, TWA_SIGNAL))
+	if (task_work_add(task, &msg->tw, TWA_SIGNAL))
 		return -EOWNERDEAD;
 
 	return IOU_ISSUE_SKIP_COMPLETE;
-- 
2.39.3 (Apple Git-146)

Re: [PATCH] io_uring/msg_ring: reuse ctx->submitter_task read using READ_ONCE instead of re-reading it

Posted by Jens Axboe 1 week, 3 days ago

On Fri, 26 Apr 2024 11:24:37 +0800, linke li wrote:
> In io_msg_exec_remote(), ctx->submitter_task is read using READ_ONCE at
> the beginning of the function, checked, and then re-read from
> ctx->submitter_task, voiding all guarantees of the checks. Reuse the value
> that was read by READ_ONCE to ensure the consistency of the task struct
> throughout the function.
> 
> 
> [...]

Applied, thanks!

[1/1] io_uring/msg_ring: reuse ctx->submitter_task read using READ_ONCE instead of re-reading it
      commit: a4d416dc60980f741f0bfa1f34a1059c498c1b4e

Best regards,
-- 
Jens Axboe