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    SubjectRe: [PATCH] drm/gma500/cdv_intel_lvds: Fix a wild pointer dereference in cdv_intel_lvds_get_modes()
    On Tue, Nov 30, 2021 at 2:26 PM Zhou Qingyang <zhou1615@umn.edu> wrote:
    >
    > In cdv_intel_lvds_get_modes(), the 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 checking 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: 6a227d5fd6c4 ("gma500: Add support for Cedarview")
    > Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>
    > ---
    > drivers/gpu/drm/gma500/cdv_intel_lvds.c | 3 +++
    > 1 file changed, 3 insertions(+)
    >
    > diff --git a/drivers/gpu/drm/gma500/cdv_intel_lvds.c b/drivers/gpu/drm/gma500/cdv_intel_lvds.c
    > index 9e1cdb11023c..56aec41ebb1a 100644
    > --- a/drivers/gpu/drm/gma500/cdv_intel_lvds.c
    > +++ b/drivers/gpu/drm/gma500/cdv_intel_lvds.c
    > @@ -310,6 +310,9 @@ static int cdv_intel_lvds_get_modes(struct drm_connector *connector)
    > if (mode_dev->panel_fixed_mode != NULL) {
    > struct drm_display_mode *mode =
    > drm_mode_duplicate(dev, mode_dev->panel_fixed_mode);
    > + if (!mode)
    > + return -ENOMEM;
    > +

    Same problem here as in the other patches.

    > drm_mode_probed_add(connector, mode);
    > return 1;
    > }
    > --
    > 2.25.1
    >

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