FAILED: patch "[PATCH] drm/amdgpu: don't walk the CS chunks when allocating them failed" failed to apply to 6.18-stable tree

FAILED: patch "[PATCH] drm/amdgpu: don't walk the CS chunks when allocating them failed" failed to apply to 6.18-stable tree

[Sasha Levin]

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 ade92d50aad6799a5a9d7e73cd1604fd0576e656
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109200547-failed-6.18-ade92d50aad6@kernel.org' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Thanks,
Sasha

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

From ade92d50aad6799a5a9d7e73cd1604fd0576e656 Mon Sep 17 00:00:00 2001
From: Jesse Zhang <Jesse.Zhang@amd.com>
Date: Tue, 3 Nov 2026 15:05:12 +0800
Subject: [PATCH] drm/amdgpu: don't walk the CS chunks when allocating them
 failed
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

amdgpu_cs_pass1() sets p->nchunks before allocating p->chunks, and the
allocation failure path skips resetting it. amdgpu_cs_parser_fini() then
frees the kdata of nchunks chunks from a NULL array. On navi48 with the
chunk array allocation failed through failslab:

  Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] SMP KASAN NOPTI
  KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
  RIP: 0010:amdgpu_cs_parser_fini+0x35d/0x710 [amdgpu]
   amdgpu_cs_ioctl+0xcae/0x7a20 [amdgpu]
   drm_ioctl_kernel+0x180/0x320 [drm]

Set nchunks once the array exists.

Fixes: d38ceaf99ed0 ("drm/amdgpu: add core driver (v4)")
Signed-off-by: Jesse Zhang <Jesse.Zhang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 0c828445757b86aaa3ed2638832d76f450022bdf)
Cc: stable@vger.kernel.org
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index f51a6c00f6ff0..1ba36dd87637b 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -203,12 +203,13 @@ static int amdgpu_cs_pass1(struct amdgpu_cs_parser *p,
 	if (IS_ERR(chunk_array))
 		return PTR_ERR(chunk_array);
 
-	p->nchunks = cs->in.num_chunks;
-	p->chunks = kvmalloc_objs(struct amdgpu_cs_chunk, p->nchunks);
+	/* parser_fini() walks nchunks chunks, set it once they exist */
+	p->chunks = kvmalloc_objs(struct amdgpu_cs_chunk, cs->in.num_chunks);
 	if (!p->chunks) {
 		ret = -ENOMEM;
 		goto free_chunk;
 	}
+	p->nchunks = cs->in.num_chunks;
 
 	for (i = 0; i < p->nchunks; i++) {
 		struct drm_amdgpu_cs_chunk __user *chunk_ptr = NULL;
-- 
2.53.0