drm/dp/mst: fix OOB reads on 2-byte fields in sideband reply parsers

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[ Upstream commit 6b89ba3dba ]

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()
   full_payload_bw_number and avail_payload_bw_number fields
 - drm_dp_sideband_parse_allocate_payload_ack()
   allocated_pbn field
 - drm_dp_sideband_parse_query_payload_ack()
   allocated_pbn field

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.

Fixes: ad7f8a1f9c ("drm/helper: add Displayport multi-stream helper (v0.6)")
Cc: <stable@vger.kernel.org> # v3.17+
Signed-off-by: Ashutosh Desai <ashutoshdesai993@gmail.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
[added fixes tag]
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patch.msgid.link/20260510203128.2884846-1-ashutoshdesai993@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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Ashutosh Desai 2026-07-31 07:33:29 -04:00 • committed by Greg Kroah-Hartman

parent d7b9b1e33b

commit 192e146c2d

1 changed files with 4 additions and 13 deletions

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drivers/gpu/drm/drm_dp_mst_topology.c

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