FAILED: patch "[PATCH] fuse: copy request headers via a stack buffer for io-uring" failed to apply to 7.1-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 7.1-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>.

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-7.1.y
git checkout FETCH_HEAD
git cherry-pick -x fd10f40af314f07b6d6e028b1ca25c8b49903aab
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026083141-whacking-derby-c87d@gregkh' --subject-prefix 'PATCH 7.1.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From fd10f40af314f07b6d6e028b1ca25c8b49903aab Mon Sep 17 00:00:00 2001
From: Xiang Mei <xmei5@asu.edu>
Date: Mon, 27 Jul 2026 16:37:04 -0700
Subject: [PATCH] fuse: copy request headers via a stack buffer for io-uring

The fuse-io-uring transport copies req->in.h out to the ring in
fuse_uring_copy_to_ring() and req->out.h back in fuse_uring_commit().
Both headers live inside the fuse_request slab object, whose cache
(fuse_req_cachep) is created without a usercopy whitelist, so copying
them directly to/from userspace trips CONFIG_HARDENED_USERCOPY and
panics:

  usercopy: Kernel memory exposure attempt detected from SLUB object
  'fuse_request' (offset 56, size 40)!
  kernel BUG at mm/usercopy.c:102!
  Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
  RIP: 0010:usercopy_abort (mm/usercopy.c:90)
  Call Trace:
   __check_heap_object (mm/slub.c:8268)
   __check_object_size (mm/usercopy.c:197 mm/usercopy.c:258 mm/usercopy.c:223)
   copy_header_to_ring (fs/fuse/dev_uring.c:618)
   fuse_uring_prepare_send (fs/fuse/dev_uring.c:776 fs/fuse/dev_uring.c:785)
   fuse_uring_send_in_task (fs/fuse/dev_uring.c:1306)
   tctx_task_work_run (io_uring/tw.c:96)
   task_work_run (kernel/task_work.c:233)
   io_run_task_work (io_uring/tw.h:84)
   io_cqring_wait (io_uring/wait.c:278)
   __do_sys_io_uring_enter (io_uring/io_uring.c:2685)
   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)

Bounce both headers through an on-stack copy so the usercopy touches
stack memory, not the slab object.

Fixes: c090c8abae4b ("fuse: Add io-uring sqe commit and fetch support")
Cc: stable@vger.kernel.org
Reported-by: Weiming Shi <bestswngs@gmail.com>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Xiang Mei <xmei5@asu.edu>
Reviewed-by: Bernd Schubert <bernd@bsbernd.com>
Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/fuse/dev_uring.c b/fs/fuse/dev_uring.c
index 1547a4f0d9b9..e22a48c9a678 100644
--- a/fs/fuse/dev_uring.c
+++ b/fs/fuse/dev_uring.c
@@ -922,6 +922,7 @@ static int fuse_uring_copy_to_ring(struct fuse_ring_ent *ent,
 				   unsigned int issue_flags)
 {
 	struct fuse_ring_queue *queue = ent->queue;
+	struct fuse_in_header in_header;
 	int err;
 
 	err = -EIO;
@@ -943,8 +944,9 @@ static int fuse_uring_copy_to_ring(struct fuse_ring_ent *ent,
 	}
 
 	/* copy fuse_in_header */
-	return copy_header_to_ring(ent, FUSE_URING_HEADER_IN_OUT, &req->in.h,
-				   sizeof(req->in.h));
+	in_header = req->in.h;
+	return copy_header_to_ring(ent, FUSE_URING_HEADER_IN_OUT, &in_header,
+				   sizeof(in_header));
 }
 
 static bool fuse_uring_req_has_copyable_payload(struct fuse_ring_ent *ent,
@@ -1151,11 +1153,13 @@ static struct fuse_req *fuse_uring_ent_assign_req(struct fuse_ring_ent *ent)
 static void fuse_uring_commit(struct fuse_ring_ent *ent, struct fuse_req *req,
 			      unsigned int issue_flags)
 {
+	struct fuse_out_header out_header;
 	ssize_t err = -EFAULT;
 
-	if (copy_header_from_ring(ent, FUSE_URING_HEADER_IN_OUT, &req->out.h,
-				  sizeof(req->out.h)))
+	if (copy_header_from_ring(ent, FUSE_URING_HEADER_IN_OUT, &out_header,
+				  sizeof(out_header)))
 		goto out;
+	req->out.h = out_header;
 
 	err = fuse_uring_out_header_has_err(&req->out.h, req);
 	if (err) {