drm: fd.o Bug #7595: Avoid u32 overflows in radeon_check_and_fixup_offset().

The overflows could cause valid offsets to get rejected under some
circumstances, e.g. when the framebuffer resides at the very end of the card's
address space.

Signed-off-by: Dave Airlie <airlied@linux.ie>

diff --git a/drivers/char/drm/radeon_state.c b/drivers/char/drm/radeon_state.c
index 0433ff8..bcfa151 100644 (file)
--- a/drivers/char/drm/radeon_state.c
+++ b/drivers/char/drm/radeon_state.c
@@ -42,7 +42,11 @@ static __inline__ int radeon_check_and_fixup_offset(drm_radeon_private_t *
                                                    drm_file_t * filp_priv,
                                                    u32 *offset)
 {
-       u32 off = *offset;
+       u64 off = *offset;
+       u32 fb_start = dev_priv->fb_location;
+       u32 fb_end = fb_start + dev_priv->fb_size - 1;
+       u32 gart_start = dev_priv->gart_vm_start;
+       u32 gart_end = gart_start + dev_priv->gart_size - 1;
        struct drm_radeon_driver_file_fields *radeon_priv;
 
        /* Hrm ... the story of the offset ... So this function converts
@@ -62,10 +66,8 @@ static __inline__ int radeon_check_and_fixup_offset(drm_radeon_private_t *
        /* First, the best case, the offset already lands in either the
         * framebuffer or the GART mapped space
         */
-       if ((off >= dev_priv->fb_location &&
-            off < (dev_priv->fb_location + dev_priv->fb_size)) ||
-           (off >= dev_priv->gart_vm_start &&
-            off < (dev_priv->gart_vm_start + dev_priv->gart_size)))
+       if ((off >= fb_start && off <= fb_end) ||
+           (off >= gart_start && off <= gart_end))
                return 0;
 
        /* Ok, that didn't happen... now check if we have a zero based
@@ -78,16 +80,13 @@ static __inline__ int radeon_check_and_fixup_offset(drm_radeon_private_t *
        }
 
        /* Finally, assume we aimed at a GART offset if beyond the fb */
-       if (off > (dev_priv->fb_location + dev_priv->fb_size))
-               off = off - (dev_priv->fb_location + dev_priv->fb_size) +
-                       dev_priv->gart_vm_start;
+       if (off > fb_end)
+               off = off - fb_end - 1 + gart_start;
 
        /* Now recheck and fail if out of bounds */
-       if ((off >= dev_priv->fb_location &&
-            off < (dev_priv->fb_location + dev_priv->fb_size)) ||
-           (off >= dev_priv->gart_vm_start &&
-            off < (dev_priv->gart_vm_start + dev_priv->gart_size))) {
-               DRM_DEBUG("offset fixed up to 0x%x\n", off);
+       if ((off >= fb_start && off <= fb_end) ||
+           (off >= gart_start && off <= gart_end)) {
+               DRM_DEBUG("offset fixed up to 0x%x\n", (unsigned int)off);
                *offset = off;
                return 0;
        }