Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E08F9480DD6; Thu, 20 Aug 2026 16:46:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787244376; cv=none; b=HLN7wzRhRcII92SWzGUdliCJrei4IUs9JQHQViVduGXvXOi0fT15snQQ4dvzgGG9pHI8nuDB3zP0RN9FLXy6mZxRyx49nYfy0quFyGgJs1sDQxnRPF1mG3lU8KMrxS5letBa+AAInhoNYSggOxNjvnMxr9eRQhSdMotp1rvzkIs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787244376; c=relaxed/simple; bh=YBDu3ACtJL/TnCmTf19yJT1AZ6Ib3FVx1qetwCQtDkw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=urp1q6DYF0L5BDNqhl/fCFymarwVlHQGpNzXL+6iYiA5VD7K4VU6v8ZTNw5qYUdqEH9X3uF5wHk6Mh5xMdxhBkiOSTeiJzG+UPaIewl57Sc9N2mI9jRtyMzJoOT20kmeu8z1RCqTCn+E+QnNh1PtmtyfaIDJ9P5f74G3c2A/GmQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=twKHvfJf; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="twKHvfJf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F066B1F000E9; Thu, 20 Aug 2026 16:46:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787244374; bh=X8EHAgjT1gdM51sc3iI9607ULqxlv1fz1leU0+GtFyU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=twKHvfJfaqNRmW4ufkltDHQz3YfqIImcLM6/1LDZKNiGiT+xPFwBLkVHjadLrz1m0 hAuNbxgCUDJTJ/zKlv+kXZThWSt2ZQgvKeJDfAi2KZlo7IkIlCBuxeqmvIxsE2j2IZ kxr6kP8K5eePVdYmwj5Roygyph/NRD+Rm61RNgFE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ashutosh Desai , Lyude Paul , Sasha Levin Subject: [PATCH 5.10 148/235] drm/dp/mst: fix OOB reads on 2-byte fields in sideband reply parsers Date: Thu, 20 Aug 2026 16:56:24 +0200 Message-ID: <20260820145220.930499351@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260820145216.426568665@linuxfoundation.org> References: <20260820145216.426568665@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ashutosh Desai [ Upstream commit 6b89ba3dba2f583626fb693e47e951ffb8bf591f ] 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: ad7f8a1f9ced ("drm/helper: add Displayport multi-stream helper (v0.6)") Cc: # v3.17+ Signed-off-by: Ashutosh Desai Reviewed-by: Lyude Paul [added fixes tag] Signed-off-by: Lyude Paul Link: https://patch.msgid.link/20260510203128.2884846-1-ashutoshdesai993@gmail.com Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/drm_dp_mst_topology.c | 17 ++++------------- 1 file changed, 4 insertions(+), 13 deletions(-) --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -920,16 +920,13 @@ static bool drm_dp_sideband_parse_enum_p repmsg->u.path_resources.port_number = (raw->msg[idx] >> 4) & 0xf; repmsg->u.path_resources.fec_capable = raw->msg[idx] & 0x1; idx++; - if (idx > raw->curlen) + if (idx + 2 > raw->curlen) goto fail_len; repmsg->u.path_resources.full_payload_bw_number = (raw->msg[idx] << 8) | (raw->msg[idx+1]); idx += 2; - if (idx > raw->curlen) + if (idx + 2 > raw->curlen) goto fail_len; repmsg->u.path_resources.avail_payload_bw_number = (raw->msg[idx] << 8) | (raw->msg[idx+1]); - idx += 2; - if (idx > raw->curlen) - goto fail_len; return true; fail_len: DRM_DEBUG_KMS("enum resource parse length fail %d %d\n", idx, raw->curlen); @@ -947,12 +944,9 @@ static bool drm_dp_sideband_parse_alloca goto fail_len; repmsg->u.allocate_payload.vcpi = raw->msg[idx]; idx++; - if (idx > raw->curlen) + if (idx + 2 > raw->curlen) goto fail_len; repmsg->u.allocate_payload.allocated_pbn = (raw->msg[idx] << 8) | (raw->msg[idx+1]); - idx += 2; - if (idx > raw->curlen) - goto fail_len; return true; fail_len: DRM_DEBUG_KMS("allocate payload parse length fail %d %d\n", idx, raw->curlen); @@ -966,12 +960,9 @@ static bool drm_dp_sideband_parse_query_ repmsg->u.query_payload.port_number = (raw->msg[idx] >> 4) & 0xf; idx++; - if (idx > raw->curlen) + if (idx + 2 > raw->curlen) goto fail_len; repmsg->u.query_payload.allocated_pbn = (raw->msg[idx] << 8) | (raw->msg[idx + 1]); - idx += 2; - if (idx > raw->curlen) - goto fail_len; return true; fail_len: DRM_DEBUG_KMS("query payload parse length fail %d %d\n", idx, raw->curlen);