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 212B43B995E; Mon, 17 Aug 2026 15:07:55 +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=1786979276; cv=none; b=mE1lvJwC72/IY9cdkptIgM/tlwXhBPWAj5HhFMWCt5WRJ7fQFV4UHyB5ilTRvhxQnVQ/dgTvqmrs5SOqILmM3VwA2jMQKPcZKEI8oQnEI+nni1e1cQ8ZmNgV/sT3oIPrsXR3q2FpNnrBNASgugDxgNXPMjDPYIxVc+Okvc31vys= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786979276; c=relaxed/simple; bh=1XorJxQJ90GNGzSPSGwpITFoieCZYtDNZDPh9rmO+Js=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YZpD70WythCqkmq36Eewc1/tcjo/NfhmuvlIQDRVl7LBFHSqkMCcbuJERfomfUXRSBVVBjGzTr6qMyio7duTyhNk6XMF3iIjMv63wCJFVEGuMpt7meseIqT8mMDYBTbU6Ldly1jAz6NUJ9e2nc5nE4vblqJsvvHcafnzUgs5siI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=yVzvCmed; 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="yVzvCmed" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7B83D1F000E9; Mon, 17 Aug 2026 15:07:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786979275; bh=lKQetaz8W5H6XgzEvJpFVV6kLigEDZUS3M3Z1+MyKSY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=yVzvCmed3Aak/Wv2T57lbix8u0GQTQtcsJEZLDUe2XiodZ3vOY82m9QlD+MGv3dqb uK8eF6oYO8cpA0uN1TRpEWcJWidc1dFsD/V7QdHwu5b+bTb8bNKmlN+zfwBCkUPY9d fKwDdpW+KyGKD5wsjpWgBjWRfVs274Bq7Uw0Xw2Y= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Ashutosh Desai , Lyude Paul Subject: [PATCH 6.1 169/609] drm/dp/mst: fix OOB reads in remote DPCD/I2C sideband reply parsers Date: Mon, 17 Aug 2026 15:27:45 +0200 Message-ID: <20260817132549.690425222@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260817132543.039278408@linuxfoundation.org> References: <20260817132543.039278408@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 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ashutosh Desai commit 1a8f537f5a1eeac941f262fe73078d6b08ba83c0 upstream. 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: Greg Kroah-Hartman --- drivers/gpu/drm/display/drm_dp_mst_topology.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c @@ -861,7 +861,7 @@ static bool drm_dp_sideband_parse_remote 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); @@ -897,7 +897,9 @@ static bool drm_dp_sideband_parse_remote 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: