Hi,
On Tue, Oct 5, 2021 at 7:29 PM Douglas Anderson dianders@chromium.org wrote:
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
This problem report came up in the context of a patch I sent out [1] and this is my attempt at a fix. The problem predates my patch, though. I don't personally know anything about DP compliance testing and what should be happening here, nor do I apparently have any hardware that actually reports a bad EDID. Thus this is just compile tested. I'm hoping that someone here can test this and make sure it seems OK to them.
Changes in v2:
- Added a comment/changed math to help make it easier to grok.
drivers/gpu/drm/drm_edid.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
Pushed this to drm-misc-fixes since the commit it fixes is fairly old.
fdc21c35aaa1 drm/edid: In connector_bad_edid() cap num_of_ext by num_blocks read
-Doug