FAILED: patch "[PATCH] fuse: wait for FR_FINISHED on abort_on_kill to prevent" failed to apply to 6.18-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 6.18-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>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 64b0b5cacbd2fea88001464cb712c9dfc795b26e
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026083101-rimless-sadness-3898@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 64b0b5cacbd2fea88001464cb712c9dfc795b26e Mon Sep 17 00:00:00 2001
From: Rochan Avlur <rochan.avlur@gmail.com>
Date: Wed, 12 Aug 2026 20:58:36 -0700
Subject: [PATCH] fuse: wait for FR_FINISHED on abort_on_kill to prevent
 use-after-free

The abort_on_kill path in request_wait_answer() calls fuse_abort_conn()
and returns without waiting for FR_FINISHED.  If fuse_dev_do_write() is
concurrently processing the same request (FR_LOCKED set), the caller
frees req->args while it is still being accessed, causing a
use-after-free.

Fix this by jumping to the existing wait_event(FR_FINISHED) instead of
returning early.  The wait will not hang because fuse_abort_conn()
ensures all requests are ended.

Reported-by: syzbot+d6540a3fa1626e11360d@syzkaller.appspotmail.com
Fixes: 204aa22a686b ("fuse: abort on fatal signal during sync init")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Rochan Avlur <rochan.avlur@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 90dceb7da571..34106f6e66a0 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -724,7 +724,7 @@ static void request_wait_answer(struct fuse_req *req)
 
 		if (req->args->abort_on_kill) {
 			fuse_chan_abort(fch, false);
-			return;
+			goto wait_for_finish;
 		}
 
 		if (test_bit(FR_URING, &req->flags))
@@ -735,6 +735,7 @@ static void request_wait_answer(struct fuse_req *req)
 			return;
 	}
 
+wait_for_finish:
 	/*
 	 * Either request is already in userspace, or it was forced.
 	 * Wait it out.