[PATCH 6.1/6.6] drm/amd/display: Add null check for head_pipe in dcn32_acquire_idle_pipe_for_head_pipe_in_layer

[PATCH 6.1/6.6] drm/amd/display: Add null check for head_pipe in dcn32_acquire_idle_pipe_for_head_pipe_in_layer

[Daniil Dulov]

From: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>

commit ac2140449184a26eac99585b7f69814bd3ba8f2d upstream.

This commit addresses a potential null pointer dereference issue in the
`dcn32_acquire_idle_pipe_for_head_pipe_in_layer` function. The issue
could occur when `head_pipe` is null.

The fix adds a check to ensure `head_pipe` is not null before asserting
it. If `head_pipe` is null, the function returns NULL to prevent a
potential null pointer dereference.

Reported by smatch:
drivers/gpu/drm/amd/amdgpu/../display/dc/resource/dcn32/dcn32_resource.c:2690 dcn32_acquire_idle_pipe_for_head_pipe_in_layer() error: we previously assumed 'head_pipe' could be null (see line 2681)

Cc: Tom Chung <chiahsuan.chung@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Roman Li <roman.li@amd.com>
Cc: Alex Hung <alex.hung@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
[ Daniil: dcn32 was moved from drivers/gpu/drm/amd/display/dc to
  drivers/gpu/drm/amd/display/dc/resource since commit
  8b8eed05a1c6 ("drm/amd/display: Refactor resource into component directory").
  The path is changed accordingly to apply the patch on 6.1.y. and 6.6.y ]
Signed-off-by: Daniil Dulov <d.dulov@aladdin.ru>
---
Backport fix for CVE-2024-49918
 drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c b/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c
index 1b1534ffee9f..591c3166a468 100644
--- a/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c
@@ -2563,8 +2563,10 @@ struct pipe_ctx *dcn32_acquire_idle_pipe_for_head_pipe_in_layer(
 	struct resource_context *old_ctx = &stream->ctx->dc->current_state->res_ctx;
 	int head_index;
 
-	if (!head_pipe)
+	if (!head_pipe) {
 		ASSERT(0);
+		return NULL;
+	}
 
 	/*
 	 * Modified from dcn20_acquire_idle_pipe_for_layer
-- 
2.34.1

Re: [PATCH 6.1/6.6] drm/amd/display: Add null check for head_pipe in dcn32_acquire_idle_pipe_for_head_pipe_in_layer

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: ac2140449184a26eac99585b7f69814bd3ba8f2d

WARNING: Author mismatch between patch and upstream commit:
Backport author: Daniil Dulov <d.dulov@aladdin.ru>
Commit author: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>

Status in newer kernel trees:
6.15.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)

Note: The patch differs from the upstream commit:
---
1:  ac2140449184 ! 1:  7a19ddcf0b97 drm/amd/display: Add null check for head_pipe in dcn32_acquire_idle_pipe_for_head_pipe_in_layer
    @@ Metadata
      ## Commit message ##
         drm/amd/display: Add null check for head_pipe in dcn32_acquire_idle_pipe_for_head_pipe_in_layer
     
    +    commit ac2140449184a26eac99585b7f69814bd3ba8f2d upstream.
    +
         This commit addresses a potential null pointer dereference issue in the
         `dcn32_acquire_idle_pipe_for_head_pipe_in_layer` function. The issue
         could occur when `head_pipe` is null.
    @@ Commit message
         Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
         Reviewed-by: Tom Chung <chiahsuan.chung@amd.com>
         Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
    +    [ Daniil: dcn32 was moved from drivers/gpu/drm/amd/display/dc to
    +      drivers/gpu/drm/amd/display/dc/resource since commit
    +      8b8eed05a1c6 ("drm/amd/display: Refactor resource into component directory").
    +      The path is changed accordingly to apply the patch on 6.1.y. and 6.6.y ]
    +    Signed-off-by: Daniil Dulov <d.dulov@aladdin.ru>
     
    - ## drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c ##
    -@@ drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c: static struct pipe_ctx *dcn32_acquire_idle_pipe_for_head_pipe_in_layer(
    + ## drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c ##
    +@@ drivers/gpu/drm/amd/display/dc/dcn32/dcn32_resource.c: static struct pipe_ctx *dcn32_acquire_idle_pipe_for_head_pipe_in_layer(
      	struct resource_context *old_ctx = &stream->ctx->dc->current_state->res_ctx;
      	int head_index;
      

---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| origin/linux-6.1.y        | Success     | Success    |
| origin/linux-6.6.y        | Success     | Success    |