Patch "drm/amd/display: Fix a NULL pointer dereference in amdgpu_dm_connector_add_common_modes()" has been added to the 5.17-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    drm/amd/display: Fix a NULL pointer dereference in amdgpu_dm_connector_add_common_modes()

to the 5.17-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-amd-display-fix-a-null-pointer-dereference-in-am.patch
and it can be found in the queue-5.17 subdirectory.

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



commit c6bcf130a8e78dcf8c044839264b505ac40bdf69
Author: Zhou Qingyang <zhou1615@xxxxxxx>
Date:   Tue Jan 25 00:57:29 2022 +0800

    drm/amd/display: Fix a NULL pointer dereference in amdgpu_dm_connector_add_common_modes()
    
    [ Upstream commit 588a70177df3b1777484267584ef38ab2ca899a2 ]
    
    In amdgpu_dm_connector_add_common_modes(), amdgpu_dm_create_common_mode()
    is assigned to mode and is passed to drm_mode_probed_add() directly after
    that. drm_mode_probed_add() passes &mode->head to list_add_tail(), and
    there is a dereference of it in list_add_tail() without recoveries, which
    could lead to NULL pointer dereference on failure of
    amdgpu_dm_create_common_mode().
    
    Fix this by adding a NULL check of mode.
    
    This bug was found by a static analyzer.
    
    Builds with 'make allyesconfig' show no new warnings,
    and our static analyzer no longer warns about this code.
    
    Fixes: e7b07ceef2a6 ("drm/amd/display: Merge amdgpu_dm_types and amdgpu_dm")
    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/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 075429bea427..5f4a346c9c2a 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -8144,6 +8144,9 @@ static void amdgpu_dm_connector_add_common_modes(struct drm_encoder *encoder,
 		mode = amdgpu_dm_create_common_mode(encoder,
 				common_modes[i].name, common_modes[i].w,
 				common_modes[i].h);
+		if (!mode)
+			continue;
+
 		drm_mode_probed_add(connector, mode);
 		amdgpu_dm_connector->num_modes++;
 	}