| Message ID | 20211130132328.129383-1-zhou1615@umn.edu (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/gma500/cdv: Fix a wild pointer dereference in cdv_intel_dp_get_modes() | expand |
On Tue, Nov 30, 2021 at 09:23:28PM +0800, Zhou Qingyang wrote: > In cdv_intel_dp_get_modes(), the third return value of > drm_mode_duplicate() is assigned to mode and used in > drm_mode_probed_add(). drm_mode_probed_add() passes mode->head to > list_add_tail(). list_add_tail() will further call __list_add() and > there is a dereference of mode->head in __list_add(), which could lead > to a wild 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_GMA500=m show no new warnings, > and our static analyzer no longer warns about this code. > > Fixes: d112a8163f83 ("gma500/cdv: Add eDP support") > Signed-off-by: Zhou Qingyang <zhou1615@umn.edu> > --- > drivers/gpu/drm/gma500/cdv_intel_dp.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/gpu/drm/gma500/cdv_intel_dp.c b/drivers/gpu/drm/gma500/cdv_intel_dp.c > index ba6ad1466374..b389008965a9 100644 > --- a/drivers/gpu/drm/gma500/cdv_intel_dp.c > +++ b/drivers/gpu/drm/gma500/cdv_intel_dp.c > @@ -1773,6 +1773,9 @@ static int cdv_intel_dp_get_modes(struct drm_connector *connector) > if (intel_dp->panel_fixed_mode != NULL) { > struct drm_display_mode *mode; > mode = drm_mode_duplicate(dev, intel_dp->panel_fixed_mode); > + if (!mode) > + return -ENOMEM; .get_modes() isn't supposed to return negative values. > + > drm_mode_probed_add(connector, mode); > return 1; > } > -- > 2.25.1
diff --git a/drivers/gpu/drm/gma500/cdv_intel_dp.c b/drivers/gpu/drm/gma500/cdv_intel_dp.c index ba6ad1466374..b389008965a9 100644 --- a/drivers/gpu/drm/gma500/cdv_intel_dp.c +++ b/drivers/gpu/drm/gma500/cdv_intel_dp.c @@ -1773,6 +1773,9 @@ static int cdv_intel_dp_get_modes(struct drm_connector *connector) if (intel_dp->panel_fixed_mode != NULL) { struct drm_display_mode *mode; mode = drm_mode_duplicate(dev, intel_dp->panel_fixed_mode); + if (!mode) + return -ENOMEM; + drm_mode_probed_add(connector, mode); return 1; }
In cdv_intel_dp_get_modes(), the third return value of drm_mode_duplicate() is assigned to mode and used in drm_mode_probed_add(). drm_mode_probed_add() passes mode->head to list_add_tail(). list_add_tail() will further call __list_add() and there is a dereference of mode->head in __list_add(), which could lead to a wild 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_GMA500=m show no new warnings, and our static analyzer no longer warns about this code. Fixes: d112a8163f83 ("gma500/cdv: Add eDP support") Signed-off-by: Zhou Qingyang <zhou1615@umn.edu> --- drivers/gpu/drm/gma500/cdv_intel_dp.c | 3 +++ 1 file changed, 3 insertions(+)