drm_parse_tiled_block() casts the DisplayID block to a
struct displayid_tiled_block and reads the full fixed layout up to
tile->topology_id[7] without checking block->num_bytes. The DisplayID
iterator only validates the declared payload length, so a crafted EDID
can advertise a tiled-display block (tag DATA_BLOCK_TILED_DISPLAY, or
DATA_BLOCK_2_TILED_DISPLAY_TOPOLOGY for v2.0) with a small num_bytes at
the end of a DisplayID extension. The read then runs past the end of the
exact-sized kmemdup()'d EDID allocation, a heap out-of-bounds read.
Reject blocks shorter than the spec's 22-byte tiled payload before
reading the fixed struct, as drm_parse_vesa_mso_data() already does.
BUG: KASAN: slab-out-of-bounds in drm_edid_connector_update
Read of size 2 at addr ffff888010077700 by task exploit/147
dump_stack_lvl (lib/dump_stack.c:94 ...)
print_report (mm/kasan/report.c:378 ...)
kasan_report (mm/kasan/report.c:595)
drm_edid_connector_update (drivers/gpu/drm/drm_edid.c:7581)
bochs_connector_helper_get_modes (drivers/gpu/drm/tiny/bochs.c:574)
drm_helper_probe_single_connector_modes
(drivers/gpu/drm/drm_probe_helper.c:426)
status_store (drivers/gpu/drm/drm_sysfs.c:219)
...
vfs_write (fs/read_write.c:595 fs/read_write.c:688)
ksys_write (fs/read_write.c:740)
Fixes: 40d9b043a89e ("drm/connector: store tile information from displayid
(v3)")
Reported-by: Weiming Shi <[email protected]>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Xiang Mei <[email protected]>
---
v2: use 22 instead of sizeof, based on the topology_id[9] fix:
https://lore.kernel.org/r/[email protected]
drivers/gpu/drm/drm_edid.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 404208bf23a6..df3c25bac761 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -7575,6 +7575,14 @@ static void drm_parse_tiled_block(struct drm_connector
*connector,
u8 num_v_tile, num_h_tile;
struct drm_tile_group *tg;
+ /* tiled block payload per spec: cap 1 + topo 3 + size 4 + bezel 5 + id
9 = 22 */
+ if (block->num_bytes < 22) {
+ drm_dbg_kms(connector->dev,
+ "[CONNECTOR:%d:%s] Unexpected tiled block size
%u\n",
+ connector->base.id, connector->name,
block->num_bytes);
+ return;
+ }
+
w = tile->tile_size[0] | tile->tile_size[1] << 8;
h = tile->tile_size[2] | tile->tile_size[3] << 8;
--
2.43.0
