From: Douglas Anderson dianders@chromium.org
commit 97794170b696856483f74b47bfb6049780d2d3a0 upstream.
In commit e11f5bd8228f ("drm: Add support for DP 1.4 Compliance edid corruption test") the function connector_bad_edid() started assuming that the memory for the EDID passed to it was big enough to hold `edid[0x7e] + 1` blocks of data (1 extra for the base block). It completely ignored the fact that the function was passed `num_blocks` which indicated how much memory had been allocated for the EDID.
Let's fix this by adding a bounds check.
This is important for handling the case where there's an error in the first block of the EDID. In that case we will call connector_bad_edid() without having re-allocated memory based on `edid[0x7e]`.
Fixes: e11f5bd8228f ("drm: Add support for DP 1.4 Compliance edid corruption test") Reported-by: Ville Syrjälä ville.syrjala@linux.intel.com Signed-off-by: Douglas Anderson dianders@chromium.org Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20211005192905.v2.1.Ib059f9c23... Signed-off-by: Dave Airlie airlied@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/drm_edid.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
--- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -1834,11 +1834,20 @@ static void connector_bad_edid(struct dr u8 *edid, int num_blocks) { int i; - u8 num_of_ext = edid[0x7e]; + u8 last_block; + + /* + * 0x7e in the EDID is the number of extension blocks. The EDID + * is 1 (base block) + num_ext_blocks big. That means we can think + * of 0x7e in the EDID of the _index_ of the last block in the + * combined chunk of memory. + */ + last_block = edid[0x7e];
/* Calculate real checksum for the last edid extension block data */ - connector->real_edid_checksum = - drm_edid_block_checksum(edid + num_of_ext * EDID_LENGTH); + if (last_block < num_blocks) + connector->real_edid_checksum = + drm_edid_block_checksum(edid + last_block * EDID_LENGTH);
if (connector->bad_edid_counter++ && !drm_debug_enabled(DRM_UT_KMS)) return;