From mboxrd@z Thu Jan 1 00:00:00 1970 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 A9CC94457A4 for ; Fri, 31 Jul 2026 15:49:43 +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=1785512984; cv=none; b=fHmqswVMLsu3C/X1lAXV33VSVFoiLzvHV3NNXfXqFuT6nBjpVSa9k9JQMc/O3wPPeXmkH5CG6SKD4mC+ML75yEgDaC+DNi0PboNrN2R5Z2hXM+9pQyoAmSntQA/EjMSQXQQlHEDsv5oCjdWyKdfpl2QuWuLo8A+u1Za6fNYiTIA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785512984; c=relaxed/simple; bh=H4BdWbGA3RWrFfuGbTJYfRbqynPPSmYhYsjE9f/bJm0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LeET92e24muzQuDDOvSuFk6YvkODj+BH42q8N4bN+W1BGZcEAfzKpqc0lJTQYoZiEq40O+JDMJrVsmR/UgpfKm8zkEIGx1eTGu5hZJUHQk5ScII5UzgS+GnULOttZx5ekRd5mkQ3YbgYO+iVjXucN+2pVDPZ+YHUHGe7Lr+udnw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cfU+nD/g; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cfU+nD/g" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CFF701F000E9; Fri, 31 Jul 2026 15:49:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785512983; bh=f4/y1vLYrd2mfMSEi6gWLlnqcbGcmhOY+anaH7N8l2I=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=cfU+nD/gQagTGjaAF1mVUgOmP52+RYEi1pMUtFWkp81NMCWoaGWKfPVQdS2TmaWol v0PipSzbSfISZ6JRyH11Mh+l0C0RS76vUPZjOhaZh9ChtMgccQ6pFal5d7amoG49Ha FhmcLg0CjrwIa993rQc8JxWNZrkYAnPZHc7+NMXRXnSRacwzmXgBSjp0sf6GulTFGC TMs57bpXbZIq1Vs7vbWmHbtG0yFiRn8XaLVQZkU+/TJ/08xEmALg8/zL0dCOa/es7f 0nDpQ+L3EN19ajqHx2Bk3qqWmZhlwYuewUC03h0D9Ci2ZYxWAQR/pmuNe9lkgFFzWW vJnthOmzV6HUA== From: Sasha Levin To: stable@vger.kernel.org Cc: Ashutosh Desai , Lyude Paul , Sasha Levin Subject: [PATCH 5.10.y] drm/dp/mst: fix OOB reads in remote DPCD/I2C sideband reply parsers Date: Fri, 31 Jul 2026 11:49:41 -0400 Message-ID: <20260731154941.601533-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026072940-amino-awaken-61dc@gregkh> References: <2026072940-amino-awaken-61dc@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Ashutosh Desai [ Upstream commit 1a8f537f5a1eeac941f262fe73078d6b08ba83c0 ] drm_dp_sideband_parse_remote_dpcd_read() reads num_bytes from the raw message and then unconditionally does: memcpy(bytes, &raw->msg[idx], num_bytes); without checking that idx + num_bytes <= raw->curlen. raw->msg[] is 256 bytes; if a malicious or misbehaving MST hub sets num_bytes larger than the remaining payload, the memcpy reads past the received data into whatever follows in raw->msg[]. drm_dp_sideband_parse_remote_i2c_read_ack() has the same flaw (noted with a /* TODO check */ comment since the code was introduced). Fix both functions by using a single combined check (idx + num_bytes > curlen) before each memcpy. Since num_bytes is u8, it is always >= 0, so this strictly subsumes the simpler idx > curlen form and 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 missing fixes tag] Signed-off-by: Lyude Paul Link: https://patch.msgid.link/20260510201733.2882224-1-ashutoshdesai993@gmail.com Signed-off-by: Sasha Levin --- drivers/gpu/drm/drm_dp_mst_topology.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c index 702ab6148425..32fa058e5f5d 100644 --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -859,7 +859,7 @@ static bool drm_dp_sideband_parse_remote_dpcd_read(struct drm_dp_sideband_msg_rx goto fail_len; repmsg->u.remote_dpcd_read_ack.num_bytes = raw->msg[idx]; idx++; - if (idx > raw->curlen) + if (idx + repmsg->u.remote_dpcd_read_ack.num_bytes > raw->curlen) goto fail_len; memcpy(repmsg->u.remote_dpcd_read_ack.bytes, &raw->msg[idx], repmsg->u.remote_dpcd_read_ack.num_bytes); @@ -895,7 +895,9 @@ static bool drm_dp_sideband_parse_remote_i2c_read_ack(struct drm_dp_sideband_msg goto fail_len; repmsg->u.remote_i2c_read_ack.num_bytes = raw->msg[idx]; idx++; - /* TODO check */ + if (idx + repmsg->u.remote_i2c_read_ack.num_bytes > raw->curlen) + goto fail_len; + memcpy(repmsg->u.remote_i2c_read_ack.bytes, &raw->msg[idx], repmsg->u.remote_i2c_read_ack.num_bytes); return true; fail_len: -- 2.53.0