[PATCH] drm/radeon: fix null pointer dereference in radeon_add_common_modes

[PATCH] drm/radeon: fix null pointer dereference in radeon_add_common_modes

[Ma Ke]

In radeon_add_common_modes(), the return value of drm_cvt_mode() is
assigned to mode, which will lead to a possible NULL pointer dereference
on failure of drm_cvt_mode(). Add a check to avoid npd.

Signed-off-by: Ma Ke <make24@iscas.ac.cn>
---
 drivers/gpu/drm/radeon/radeon_connectors.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c
index b84b58926106..71ddc4672850 100644
--- a/drivers/gpu/drm/radeon/radeon_connectors.c
+++ b/drivers/gpu/drm/radeon/radeon_connectors.c
@@ -520,6 +520,8 @@ static void radeon_add_common_modes(struct drm_encoder *encoder, struct drm_conn
 			continue;
 
 		mode = drm_cvt_mode(dev, common_modes[i].w, common_modes[i].h, 60, false, false, false);
+		if (!mode)
+			continue;
 		drm_mode_probed_add(connector, mode);
 	}
 }
-- 
2.25.1

Re: [PATCH] drm/radeon: fix null pointer dereference in radeon_add_common_modes

[Markus Elfring]

> In radeon_add_common_modes(), the return value of drm_cvt_mode() is
> assigned to mode, which will lead to a possible NULL pointer dereference
> on failure of drm_cvt_mode(). Add a check to avoid npd.

1. Can a wording approach (like the following) be a better change description?

   A null pointer is stored in the local variable “mode” after a call
   of the function “drm_cvt_mode” failed. This pointer was passed to
   a subsequent call of the function “drm_mode_probed_add” where an undesirable
   dereference will be performed then.
   Thus add a corresponding return value check.


2. Would you like to add any tags (like “Fixes” and “Cc”) accordingly?


3. How do you think about to append parentheses to the function name
   in the summary phrase?


Regards,
Markus