Quoting Ville Syrjala (2018-10-23 17:02:01)
> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> Let's try to make sure the fb offset computations never hit
> an integer overflow by making sure the entire fb stays
> below 32bits. framebuffer_check() in the core already does
> the same check, but as it doesn't know about tiling some things
> can slip through. Repeat the check in the driver with tiling
> taken into account.
>
> v2: Use add_overflows() after massaging it to work for me (Chris)
> v3: Call it add_overflow_t() to match min_t() & co. (Chris)
>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_utils.h | 11 +++++++----
> drivers/gpu/drm/i915/intel_display.c | 18 +++++++++++++++++-
> 2 files changed, 24 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h
> index 5858a43e19da..9726df37c4c4 100644
> --- a/drivers/gpu/drm/i915/i915_utils.h
> +++ b/drivers/gpu/drm/i915/i915_utils.h
> @@ -44,16 +44,19 @@
> __stringify(x), (long)(x))
>
> #if defined(GCC_VERSION) && GCC_VERSION >= 70000
> -#define add_overflows(A, B) \
> - __builtin_add_overflow_p((A), (B), (typeof((A) + (B)))0)
> +#define add_overflows_t(T, A, B) \
> + __builtin_add_overflow_p((A), (B), (T)0)
> #else
> -#define add_overflows(A, B) ({ \
> +#define add_overflows_t(T, A, B) ({ \
> typeof(A) a = (A); \
> typeof(B) b = (B); \
> - a + b < a; \
> + (T)(a + b) < a; \
> })
> #endif
>
> +#define add_overflows(A, B) \
> + add_overflows_t(typeof((A) + (B)), (A), (B))
> +
> #define range_overflows(start, size, max) ({ \
> typeof(start) start__ = (start); \
> typeof(size) size__ = (size); \
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 969d22ca8dcd..e520facc23e1 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -2351,10 +2351,26 @@ static int intel_fb_offset_to_xy(int *x, int *y,
> int color_plane)
> {
> struct drm_i915_private *dev_priv = to_i915(fb->dev);
> + unsigned int height;
>
> if (fb->modifier != DRM_FORMAT_MOD_LINEAR &&
> - fb->offsets[color_plane] % intel_tile_size(dev_priv))
> + fb->offsets[color_plane] % intel_tile_size(dev_priv)) {
> + DRM_DEBUG_KMS("Misaligned offset 0x%08x for color plane %d\n",
> + fb->offsets[color_plane], color_plane);
> return -EINVAL;
> + }
> +
> + height = drm_framebuffer_plane_height(fb->height, fb, color_plane);
> + height = ALIGN(height, intel_tile_height(fb, color_plane));
fb height is limited to u16 or thereabouts?
> +
> + /* Catch potential overflows early */
> + if (add_overflows_t(u32, mul_u32_u32(height, fb->pitches[color_plane]),
> + fb->offsets[color_plane])) {
> + DRM_DEBUG_KMS("Bad offset 0x%08x or pitch %d for color plane %d\n",
> + fb->offsets[color_plane], fb->pitches[color_plane],
> + color_plane);
> + return -ERANGE;
> + }
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
-Chris
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