diff options
author | Thomas Zimmermann <tzimmermann@suse.de> | 2022-06-21 13:46:17 +0300 |
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committer | Thomas Zimmermann <tzimmermann@suse.de> | 2022-06-27 12:10:43 +0300 |
commit | ae25885bdf59fde40726863c57fd20e4a0642183 (patch) | |
tree | 61368795e886d34ff2e156e808ec211f2b68f6f8 /drivers/gpu/drm/drm_fb_helper.c | |
parent | d173780620792c725506b0f3c5ec52c7fbac1db0 (diff) | |
download | linux-ae25885bdf59fde40726863c57fd20e4a0642183.tar.xz |
drm/fb-helper: Fix out-of-bounds access
Clip memory range to screen-buffer size to avoid out-of-bounds access
in fbdev deferred I/O's damage handling.
Fbdev's deferred I/O can only track pages. From the range of pages, the
damage handler computes the clipping rectangle for the display update.
If the fbdev screen buffer ends near the beginning of a page, that page
could contain more scanlines. The damage handler would then track these
non-existing scanlines as dirty and provoke an out-of-bounds access
during the screen update. Hence, clip the maximum memory range to the
size of the screen buffer.
While at it, rename the variables min/max to min_off/max_off in
drm_fb_helper_deferred_io(). This avoids confusion with the macros of
the same name.
Reported-by: Nuno Gonçalves <nunojpg@gmail.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: Nuno Gonçalves <nunojpg@gmail.com>
Fixes: 67b723f5b742 ("drm/fb-helper: Calculate damaged area in separate helper")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: <stable@vger.kernel.org> # v5.18+
Link: https://patchwork.freedesktop.org/patch/msgid/20220621104617.8817-1-tzimmermann@suse.de
Diffstat (limited to 'drivers/gpu/drm/drm_fb_helper.c')
-rw-r--r-- | drivers/gpu/drm/drm_fb_helper.c | 27 |
1 files changed, 19 insertions, 8 deletions
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 5e9c373e6b88..2d4cee6a10ff 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -681,7 +681,11 @@ static void drm_fb_helper_damage(struct fb_info *info, u32 x, u32 y, schedule_work(&helper->damage_work); } -/* Convert memory region into area of scanlines and pixels per scanline */ +/* + * Convert memory region into area of scanlines and pixels per + * scanline. The parameters off and len must not reach beyond + * the end of the framebuffer. + */ static void drm_fb_helper_memory_range_to_clip(struct fb_info *info, off_t off, size_t len, struct drm_rect *clip) { @@ -716,22 +720,29 @@ static void drm_fb_helper_memory_range_to_clip(struct fb_info *info, off_t off, */ void drm_fb_helper_deferred_io(struct fb_info *info, struct list_head *pagereflist) { - unsigned long start, end, min, max; + unsigned long start, end, min_off, max_off; struct fb_deferred_io_pageref *pageref; struct drm_rect damage_area; - min = ULONG_MAX; - max = 0; + min_off = ULONG_MAX; + max_off = 0; list_for_each_entry(pageref, pagereflist, list) { start = pageref->offset; end = start + PAGE_SIZE; - min = min(min, start); - max = max(max, end); + min_off = min(min_off, start); + max_off = max(max_off, end); } - if (min >= max) + if (min_off >= max_off) return; - drm_fb_helper_memory_range_to_clip(info, min, max - min, &damage_area); + /* + * As we can only track pages, we might reach beyond the end + * of the screen and account for non-existing scanlines. Hence, + * keep the covered memory area within the screen buffer. + */ + max_off = min(max_off, info->screen_size); + + drm_fb_helper_memory_range_to_clip(info, min_off, max_off - min_off, &damage_area); drm_fb_helper_damage(info, damage_area.x1, damage_area.y1, drm_rect_width(&damage_area), drm_rect_height(&damage_area)); |