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SubjectRe: [PATCH][next] drm: fix null pointer dereference on null state pointer
On Sat, Dec 22, 2018 at 01:00:46PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
>
> In the case where state cannot be allocated, the current exit path via
> label 'out' will dereference the null state pointer when calling
> drm_atomic_state_put. Fix this by adding a new error exit label and
> jumping to this to avoid the drm_atomic_state_put.
>
> Detected by CoverityScan, CID#1476034 ("Dereference after null check")
>
> Fixes: b9fc5e01d1ce ("drm: Add helper to implement legacy dirtyfb")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>

Looks correct to me, merged into drm-misc-next-fixes for 4.21.

Thanks, Daniel

> ---
> drivers/gpu/drm/drm_damage_helper.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_damage_helper.c b/drivers/gpu/drm/drm_damage_helper.c
> index d2a1c7372f36..31032407254d 100644
> --- a/drivers/gpu/drm/drm_damage_helper.c
> +++ b/drivers/gpu/drm/drm_damage_helper.c
> @@ -178,7 +178,7 @@ int drm_atomic_helper_dirtyfb(struct drm_framebuffer *fb,
> state = drm_atomic_state_alloc(fb->dev);
> if (!state) {
> ret = -ENOMEM;
> - goto out;
> + goto out_drop_locks;
> }
> state->acquire_ctx = &ctx;
>
> @@ -238,6 +238,7 @@ int drm_atomic_helper_dirtyfb(struct drm_framebuffer *fb,
> kfree(rects);
> drm_atomic_state_put(state);
>
> +out_drop_locks:
> drm_modeset_drop_locks(&ctx);
> drm_modeset_acquire_fini(&ctx);
>
> --
> 2.19.1
>

--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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