drm/amd/display: fix a Null pointer dereference vulnerability

[Why]
A null pointer dereference vulnerability exists in the AMD display driver's
(DC module) cleanup function dc_destruct().
When display control context (dc->ctx) construction fails
(due to memory allocation failure), this pointer remains NULL.
During subsequent error handling when dc_destruct() is called,
there's no NULL check before dereferencing the perf_trace member
(dc->ctx->perf_trace), causing a kernel null pointer dereference crash.

[How]
Check if dc->ctx is non-NULL before dereferencing.

Link: https://lore.kernel.org/r/tencent_54FF4252EDFB6533090A491A25EEF3EDBF06@qq.com
Co-developed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
(Updated commit text and removed unnecessary error message)
Signed-off-by: Siyang Liu <Security@tencent.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Reviewed-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 9dd8e2ba268c636c240a918e0a31e6feaee19404)
Cc: stable@vger.kernel.org

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
index 28aca7017f0f7d6d4628d5757c5b86ad6b3551cd..9ab0ee20ca6fe2c10e91f7a7981166abaf0e120e 100644 (file)
--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -938,17 +938,18 @@ static void dc_destruct(struct dc *dc)
        if (dc->link_srv)
                link_destroy_link_service(&dc->link_srv);
 
-       if (dc->ctx->gpio_service)
-               dal_gpio_service_destroy(&dc->ctx->gpio_service);
+       if (dc->ctx) {
+               if (dc->ctx->gpio_service)
+                       dal_gpio_service_destroy(&dc->ctx->gpio_service);
 
-       if (dc->ctx->created_bios)
-               dal_bios_parser_destroy(&dc->ctx->dc_bios);
+               if (dc->ctx->created_bios)
+                       dal_bios_parser_destroy(&dc->ctx->dc_bios);
+               kfree(dc->ctx->logger);
+               dc_perf_trace_destroy(&dc->ctx->perf_trace);
 
-       kfree(dc->ctx->logger);
-       dc_perf_trace_destroy(&dc->ctx->perf_trace);
-
-       kfree(dc->ctx);
-       dc->ctx = NULL;
+               kfree(dc->ctx);
+               dc->ctx = NULL;
+       }
 
        kfree(dc->bw_vbios);
        dc->bw_vbios = NULL;