In radeon_fp_native_mode(), the return value of drm_mode_duplicate() is assigned to mode and there is a dereference of it in radeon_fp_native_mode(), which could lead to a NULL pointer dereference on failure of drm_mode_duplicate().

Fix this bug by adding 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_RADEON=m show no new warnings, and our static analyzer no longer warns about this code.

Fixes: d2efdf6d6f42 ("drm/radeon/kms: add cvt mode if we only have lvds w/h and no edid (v4)") Signed-off-by: Zhou Qingyang zhou1615@umn.edu --- Changes in v2: - Add a similar check in else clause

drivers/gpu/drm/radeon/radeon_connectors.c | 6 ++++++ 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c index 607ad5620bd9..7953830cc8b5 100644 --- a/drivers/gpu/drm/radeon/radeon_connectors.c +++ b/drivers/gpu/drm/radeon/radeon_connectors.c @@ -473,6 +473,9 @@ static struct drm_display_mode *radeon_fp_native_mode(struct drm_encoder *encode 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);

@@ -487,6 +490,9 @@ static struct drm_display_mode *radeon_fp_native_mode(struct drm_encoder *encode * 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); }