Patch "drm/amdgpu: Fix a NULL pointer dereference in amdgpu_connector_lcd_native_mode()" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    drm/amdgpu: Fix a NULL pointer dereference in amdgpu_connector_lcd_native_mode()

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-amdgpu-fix-a-null-pointer-dereference-in-amdgpu_.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 12dea635d082a3da8e887c33bbea9dcf54a79f24
Author: Zhou Qingyang <zhou1615@xxxxxxx>
Date:   Fri Dec 3 00:17:36 2021 +0800

    drm/amdgpu: Fix a NULL pointer dereference in amdgpu_connector_lcd_native_mode()
    
    [ Upstream commit b220110e4cd442156f36e1d9b4914bb9e87b0d00 ]
    
    In amdgpu_connector_lcd_native_mode(), the return value of
    drm_mode_duplicate() is assigned to mode, and there is a dereference
    of it in amdgpu_connector_lcd_native_mode(), which will lead to a NULL
    pointer dereference on failure of drm_mode_duplicate().
    
    Fix this bug add a check of mode.
    
    This bug was found by a static analyzer. The analysis employs
    differential checking to identify inconsistent security operations
    (e.g., checks or kfrees) between two code paths and confirms that the
    inconsistent operations are not recovered in the current function or
    the callers, so they constitute bugs.
    
    Note that, as a bug found by static analysis, it can be a false
    positive or hard to trigger. Multiple researchers have cross-reviewed
    the bug.
    
    Builds with CONFIG_DRM_AMDGPU=m show no new warnings, and
    our static analyzer no longer warns about this code.
    
    Fixes: d38ceaf99ed0 ("drm/amdgpu: add core driver (v4)")
    Signed-off-by: Zhou Qingyang <zhou1615@xxxxxxx>
    Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
index 0d39e386f6e9c..0e1cacf731698 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_connectors.c
@@ -389,6 +389,9 @@ amdgpu_connector_lcd_native_mode(struct drm_encoder *encoder)
 	    native_mode->vdisplay != 0 &&
 	    native_mode->clock != 0) {
 		mode = drm_mode_duplicate(dev, native_mode);
+		if (!mode)
+			return NULL;
+
 		mode->type = DRM_MODE_TYPE_PREFERRED | DRM_MODE_TYPE_DRIVER;
 		drm_mode_set_name(mode);
 
@@ -403,6 +406,9 @@ amdgpu_connector_lcd_native_mode(struct drm_encoder *encoder)
 		 * simpler.
 		 */
 		mode = drm_cvt_mode(dev, native_mode->hdisplay, native_mode->vdisplay, 60, true, false, false);
+		if (!mode)
+			return NULL;
+
 		mode->type = DRM_MODE_TYPE_PREFERRED | DRM_MODE_TYPE_DRIVER;
 		DRM_DEBUG_KMS("Adding cvt approximation of native panel mode %s\n", mode->name);
 	}