FAILED: patch "[PATCH] accel/amdxdna: return early from a zero-length flush" 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 dc14753664240cedf669623b27ae9922b0618b25
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026090959-anyhow-crinkly-25f7@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From dc14753664240cedf669623b27ae9922b0618b25 Mon Sep 17 00:00:00 2001
From: Taimuraz Kaitmazov <taimuraz@kaitmazov.com>
Date: Tue, 18 Aug 2026 02:06:55 +0300
Subject: [PATCH] accel/amdxdna: return early from a zero-length flush

SYNC_BO does not constrain its size, so a request for zero bytes reaches
drm_clflush_virt_range(), which ends with an unconditional
clflushopt(end - 1). For an empty range that is the byte before the
mapping, and abo->mem.kva comes from vmap(), so the access lands in the
guard page below the vmalloc area and faults:

  BUG: unable to handle page fault for address: ffffd16fbbc70fff
  #PF: supervisor read access in kernel mode
  Oops: Oops: 0000 [#1] SMP NOPTI
  CPU: 7 UID: 1000 Comm: sync_bo_probe
  RIP: 0010:drm_clflush_virt_range+0x3c/0x70
  Call Trace:
   amdxdna_drm_sync_bo_ioctl+0x124/0x430 [amdxdna]
   drm_ioctl+0x301/0x4c0
   __x64_sys_ioctl+0x115/0x2f0
   do_syscall_64+0xa6/0x3d0

Any process that can open the render node can do this. Reproduced 3 of 3
times on a Strix Point NPU (1022:17f0), by calling SYNC_BO with size 0 on
an AMDXDNA_BO_SHARE object. The import arm takes the same request but
flushes the whole scatterlist, so it survives it.

Nothing needs flushing for an empty range, so answer before choosing a
path.

Fixes: e252e3f3488a ("accel/amdxdna: Revise device bo creation and free")
Cc: stable@vger.kernel.org
Signed-off-by: Taimuraz Kaitmazov <taimuraz@kaitmazov.com>
Reviewed-by: Lizhi Hou <lizhi.hou@amd.com>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260817230655.356785-1-taimuraz@kaitmazov.com

diff --git a/drivers/accel/amdxdna/amdxdna_gem.c b/drivers/accel/amdxdna/amdxdna_gem.c
index 1c63eff0a4a8..2a16de96e6a4 100644
--- a/drivers/accel/amdxdna/amdxdna_gem.c
+++ b/drivers/accel/amdxdna/amdxdna_gem.c
@@ -1247,6 +1247,9 @@ static int amdxdna_flush_bo(struct amdxdna_gem_obj *abo, u64 offset, u64 size)
 		return -EINVAL;
 
 	size = min(abo->mem.size, end) - offset;
+	if (!size)
+		return 0;
+
 	if (is_import_bo(abo))
 		drm_clflush_sg(abo->base.sgt);
 	else if (amdxdna_gem_vmap(abo))