This is a note to let you know that I've just added the patch titled io_uring/msg_ring: don't leave potentially dangling ->tctx pointer to the 6.13-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: io_uring-msg_ring-don-t-leave-potentially-dangling-t.patch and it can be found in the queue-6.13 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit e72541e4993764d9b61f1055210d79a9647b88ce Author: Jens Axboe <axboe@xxxxxxxxx> Date: Wed Jan 22 17:03:28 2025 -0700 io_uring/msg_ring: don't leave potentially dangling ->tctx pointer [ Upstream commit 69a62e03f896a7382671877b6ad6aab87c53e9c3 ] For remote posting of messages, req->tctx is assigned even though it is never used. Rather than leave a dangling pointer, just clear it to NULL and use the previous check for a valid submitter_task to gate on whether or not the request should be terminated. Reported-by: Jann Horn <jannh@xxxxxxxxxx> Fixes: b6f58a3f4aa8 ("io_uring: move struct io_kiocb from task_struct to io_uring_task") Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/io_uring/msg_ring.c b/io_uring/msg_ring.c index 333c220d322a9..800cd48001e6e 100644 --- a/io_uring/msg_ring.c +++ b/io_uring/msg_ring.c @@ -89,8 +89,7 @@ static void io_msg_tw_complete(struct io_kiocb *req, struct io_tw_state *ts) static int io_msg_remote_post(struct io_ring_ctx *ctx, struct io_kiocb *req, int res, u32 cflags, u64 user_data) { - req->tctx = READ_ONCE(ctx->submitter_task->io_uring); - if (!req->tctx) { + if (!READ_ONCE(ctx->submitter_task)) { kmem_cache_free(req_cachep, req); return -EOWNERDEAD; } @@ -98,6 +97,7 @@ static int io_msg_remote_post(struct io_ring_ctx *ctx, struct io_kiocb *req, io_req_set_res(req, res, cflags); percpu_ref_get(&ctx->refs); req->ctx = ctx; + req->tctx = NULL; req->io_task_work.func = io_msg_tw_complete; io_req_task_work_add_remote(req, ctx, IOU_F_TWQ_LAZY_WAKE); return 0;