FAILED: patch "[PATCH] io_uring/msg_ring: fix remote queue to disabled ring" failed to apply to 6.1-stable tree

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 <[email protected]>.

Possible dependencies:

8579538c89e3 ("io_uring/msg_ring: fix remote queue to disabled ring") 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 8579538c89e33ce78be2feb41e07489c8cbf8f31 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <[email protected]>
Date: Fri, 20 Jan 2023 16:38:06 +0000
Subject: [PATCH] io_uring/msg_ring: fix remote queue to disabled ring

IORING_SETUP_R_DISABLED rings don't have the submitter task set, so it's not always safe to use ->submitter_task. Disallow posting msg_ring messaged to disabled rings. Also add task NULL check for loosy sync around testing for IORING_SETUP_R_DISABLED.

index 2ac1cd8d23ea..0a4efada9b3c 100644
@@ -3674,7 +3674,7 @@ static __cold int io_uring_create(unsigned entries, struct io_uring_params *p,
 
 	if (ctx->flags & IORING_SETUP_SINGLE_ISSUER
 	    && !(ctx->flags & IORING_SETUP_R_DISABLED))
-		ctx->submitter_task = get_task_struct(current);
+		WRITE_ONCE(ctx->submitter_task, get_task_struct(current));
 
 	file = io_uring_get_file(ctx);
 	if (IS_ERR(file)) {

@@ -3868,7 +3868,7 @@ static int io_register_enable_rings(struct io_ring_ctx *ctx)
 		return -EBADFD;
 
 	if (ctx->flags & IORING_SETUP_SINGLE_ISSUER && !ctx->submitter_task)
-		ctx->submitter_task = get_task_struct(current);
+		WRITE_ONCE(ctx->submitter_task, get_task_struct(current));
 
 	if (ctx->restrictions.registered)
 		ctx->restricted = 1;

index bb868447dcdf..15602a136821 100644
@@ -69,6 +69,10 @@ 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);
+	struct task_struct *task = READ_ONCE(ctx->submitter_task);
+
+	if (unlikely(!task))
+		return -EOWNERDEAD;
 
 	init_task_work(&msg->tw, func);
 	if (task_work_add(ctx->submitter_task, &msg->tw, TWA_SIGNAL))

@@ -114,6 +118,8 @@ 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->flags & IORING_SETUP_R_DISABLED)
+		return -EBADFD;
 
 	if (io_msg_need_remote(target_ctx))
 		return io_msg_exec_remote(req, io_msg_tw_complete);

@@ -206,6 +212,8 @@ static int io_msg_send_fd(struct io_kiocb *req, unsigned int issue_flags)
 
 	if (target_ctx == ctx)
 		return -EINVAL;
+	if (target_ctx->flags & IORING_SETUP_R_DISABLED)
+		return -EBADFD;
 	if (!src_file) {
 		src_file = io_msg_grab_file(req, issue_flags);
 		if (!src_file)