In the Linux kernel, the following vulnerability has been resolved:
drm/dp/mst: fix OOB reads on 2-byte fields in sideband reply parsers
Three sideband reply parsers read 16-bit fields as:
val = (raw->msg[idx] << 8) | (raw->msg[idx+1]);
and check bounds only after the fact. When idx == raw->curlen, raw->msg[idx+1] reads one byte past the received message data into the following struct fields (curchunk_len, curchunk_idx, curlen).
Affected functions:
- drm_dp_sideband_parse_enum_path_resources_ack()
- drm_dp_sideband_parse_allocate_payload_ack()
- drm_dp_sideband_parse_query_payload_ack()
Fix by using a single combined check (idx + 2 > curlen) before each 2-byte read. Since the check is strictly tighter than idx > curlen, no separate step is needed.
[added fixes tag]