FAILED: patch "[PATCH] io_uring/msg_ring: fix flagging remote execution" failed to apply to 6.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

Possible dependencies:

56d8e3180c06 ("io_uring/msg_ring: fix flagging remote execution")
423d5081d045 ("io_uring/msg_ring: move double lock/unlock helpers higher up")
761c61c15903 ("io_uring/msg_ring: flag target ring as having task_work, if needed")
6d043ee1164c ("io_uring: do msg_ring in target task via tw")
172113101641 ("io_uring: extract a io_msg_install_complete helper")
11373026f296 ("io_uring: get rid of double locking")
4c979eaefa43 ("io_uring: improve io_double_lock_ctx fail handling")
b529c96a896b ("io_uring: remove overflow param from io_post_aux_cqe")
a77ab745f28d ("io_uring: make io_fill_cqe_aux static")
9b8c54755a2b ("io_uring: add io_aux_cqe which allows deferred completion")
931147ddfa6e ("io_uring: allow defer completion for aux posted cqes")
1bec951c3809 ("io_uring: iopoll protect complete_post")
fa18fa2272c7 ("io_uring: inline __io_req_complete_put()")
f9d567c75ec2 ("io_uring: inline __io_req_complete_post()")
e2ad599d1ed3 ("io_uring: allow multishot recv CQEs to overflow")
515e26961295 ("io_uring: revert "io_uring fix multishot accept ordering"")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 56d8e3180c065c9b78ed77afcd0cf99677a4e22f Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <asml.silence@gmail.com>
Date: Fri, 20 Jan 2023 16:38:05 +0000
Subject: [PATCH] io_uring/msg_ring: fix flagging remote execution

There is a couple of problems with queueing a tw in io_msg_ring_data()
for remote execution. First, once we queue it the target ring can
go away and so setting IORING_SQ_TASKRUN there is not safe. Secondly,
the userspace might not expect IORING_SQ_TASKRUN.

Extract a helper and uniformly use TWA_SIGNAL without TWA_SIGNAL_NO_IPI
tricks for now, just as it was done in the original patch.

Cc: stable@vger.kernel.org
Fixes: 6d043ee1164ca ("io_uring: do msg_ring in target task via tw")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/msg_ring.c b/io_uring/msg_ring.c
index a333781565d3..bb868447dcdf 100644
--- a/io_uring/msg_ring.c
+++ b/io_uring/msg_ring.c
@@ -58,6 +58,25 @@ void io_msg_ring_cleanup(struct io_kiocb *req)
 	msg->src_file = NULL;
 }
 
+static inline bool io_msg_need_remote(struct io_ring_ctx *target_ctx)
+{
+	if (!target_ctx->task_complete)
+		return false;
+	return current != target_ctx->submitter_task;
+}
+
+static int io_msg_exec_remote(struct io_kiocb *req, task_work_func_t func)
+{
+	struct io_ring_ctx *ctx = req->file->private_data;
+	struct io_msg *msg = io_kiocb_to_cmd(req, struct io_msg);
+
+	init_task_work(&msg->tw, func);
+	if (task_work_add(ctx->submitter_task, &msg->tw, TWA_SIGNAL))
+		return -EOWNERDEAD;
+
+	return IOU_ISSUE_SKIP_COMPLETE;
+}
+
 static void io_msg_tw_complete(struct callback_head *head)
 {
 	struct io_msg *msg = container_of(head, struct io_msg, tw);
@@ -96,15 +115,8 @@ static int io_msg_ring_data(struct io_kiocb *req, unsigned int issue_flags)
 	if (msg->src_fd || msg->dst_fd || msg->flags)
 		return -EINVAL;
 
-	if (target_ctx->task_complete && current != target_ctx->submitter_task) {
-		init_task_work(&msg->tw, io_msg_tw_complete);
-		if (task_work_add(target_ctx->submitter_task, &msg->tw,
-				  TWA_SIGNAL_NO_IPI))
-			return -EOWNERDEAD;
-
-		atomic_or(IORING_SQ_TASKRUN, &target_ctx->rings->sq_flags);
-		return IOU_ISSUE_SKIP_COMPLETE;
-	}
+	if (io_msg_need_remote(target_ctx))
+		return io_msg_exec_remote(req, io_msg_tw_complete);
 
 	ret = -EOVERFLOW;
 	if (target_ctx->flags & IORING_SETUP_IOPOLL) {
@@ -202,14 +214,8 @@ static int io_msg_send_fd(struct io_kiocb *req, unsigned int issue_flags)
 		req->flags |= REQ_F_NEED_CLEANUP;
 	}
 
-	if (target_ctx->task_complete && current != target_ctx->submitter_task) {
-		init_task_work(&msg->tw, io_msg_tw_fd_complete);
-		if (task_work_add(target_ctx->submitter_task, &msg->tw,
-				  TWA_SIGNAL))
-			return -EOWNERDEAD;
-
-		return IOU_ISSUE_SKIP_COMPLETE;
-	}
+	if (io_msg_need_remote(target_ctx))
+		return io_msg_exec_remote(req, io_msg_tw_fd_complete);
 	return io_msg_install_complete(req, issue_flags);
 }