From nobody Sat Jun 20 20:54:04 2026 Received: from mail-qk1-f180.google.com (mail-qk1-f180.google.com [209.85.222.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2695E282F22 for ; Fri, 10 Apr 2026 03:41:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.222.180 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775792498; cv=none; b=vBzAWzMyUpwDBf2Awv/rIY0swS+oacydZQ1b4pCFiTM3ZuEtk6I0mL81xBTjLGEJKklVxk9JcPkWbwVoQXG6CNs7Ide7TTCcKWKeB2qWbXkj3r1jMt1VJiPjMn3A6F1EpTaP2aqEocCT9SqrY62B95TZgiEKQA/gPMyRP6QL/7o= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775792498; c=relaxed/simple; bh=yacRtHghybVKHGga7ubCAlh8TZwoFTh/bEIO67P5Uvc=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=CEG5r1mNcBfb88l1tNE7FU07x3n5Z+On2Gbr0+V3ZWOs4mnQ+AutcMNzqzpAPCnkuQW3994968SUzRGDsdOi3KjRMnDY0QBXBBjynIExXkefFXSnAsIe58VtoBYlw7Hqfk7NpZWoxRu8Xebb9TN3uxeiivmf7dTZ/GAM3/AGDLY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=H3DeWPbQ; arc=none smtp.client-ip=209.85.222.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="H3DeWPbQ" Received: by mail-qk1-f180.google.com with SMTP id af79cd13be357-8cb38e86cf2so143518985a.1 for ; Thu, 09 Apr 2026 20:41:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1775792496; x=1776397296; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=Oc84VNSkcWZZsnzjTmO0R+FA4pK9rFcbo2uFSa1A1Ms=; b=H3DeWPbQqEhSuthRdDW0hnxp9JGuwJI5ySaJB8cb6BsoWghoFXFN8kJJ7kac5jyvH1 icLluVgpe5+LmRxKjWFMA8uHwA0kxsYVhWg/kQqYqiylsYcuq0RjvY4QKzeJ532JvH/N fzn4ec/ww9ouApw/ZTYwqa2sxLWTmB/bpOBR0pNp5YRjo8t4gvWzi73o+mB+cJoTV2fs D6qhBIOiQGTEONXGpxKt0hzK0c+K0rMFc1Us4HnTCAZftSLW33DpF54QLMzTY55tEahH qD0A1gGZ5bt4L5JjDseELQlclXv4Mk5qe96jOSshTStpmGEHphrl0KD9ULRGGdhI+whi A0NQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1775792496; x=1776397296; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-gg:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Oc84VNSkcWZZsnzjTmO0R+FA4pK9rFcbo2uFSa1A1Ms=; b=ENPdSx9kzamhvl986ypV5SbmrFiBAhg0lHT6HxEjczlTbBrEPf5ezWRGh2vNafSJcd CpEwOAvZCHs0aCCx0WjExLKS8H/LOslY9okmUGGchwSZvD+S9x/x2swwW2rPxJTlusgo ap+bVFAuZ7Neqw87woXY4NlaNPQtUl0qsQsajo07pj+4OjlGkCO+5ELG7o0AKRWLaH4A HVCGBLtE7glCUc2S0lFf/r/nVAtgDHI3ohv9zMC5lnHSbYjo2eymdzeEvvZ7RHoluRci hmvPJKQUK4F8pLJpIjSCzR/N/PQd++RCK7S/ZNvt5Eypav+Zk3/bbWTKfye9///rvmtn brMA== X-Forwarded-Encrypted: i=1; AJvYcCUP6JlRRiAsbprdNOpkpxCmN2XzIUe7yG/H1pi8MG3JojW4rc4EgSEW4xJtNNLNt8QSnHEBMszPorML/WM=@vger.kernel.org X-Gm-Message-State: AOJu0Yz0ZxTPsZSPmjShgYZnTxbWxKD6KQck8dEvfuBQZ1JwO6mLnkCh FFtvKRtiZP0jMDuMoJkNmERdtJwW3edhCnuqI5saG/p1PSOLr8iFvWbS X-Gm-Gg: AeBDietG0wRkvr/2/cNtJYkzdaS940Fyh6EZ119w0ZI91xEMJrEPb/DZXyDRQfZ4Xb5 OpL0jby5Yz2ks5OJc+seBaQH9uFHWUmhF32FN9oKf0vfRvqIAOGZm0b7ALobu2nznNMpZ4qQZxo cEjDt1OMOZ1tuBSqtG77kdf2qrFVZ/aixCLHRnCoS13dOVvnOK6ISivjx58BUv+x9TTdK9rnwXH cAMFMTorHLuaC7xUlzfU5OZzE0S8t3SX2pY8+TiBTT7jEVE9cdXSm1MXB5ItA+OjNxzFp747Uof wbDzfLI7GYl/0ne7UKMdzh8ODs5rMHpSSMgh6altZcT0sFfgP1p4d3ecf4hXi46JU2r6wE1fjs4 Emqtne+vKski7TOgBk6lAp/ClJ+t5Bv115IBYLLUaj8cw//Of6uyCb52xDwop6UKApxi+vH/n1x jtt1vFMUPW9fcpVSOgGEbId9rUMm5Fj61l/xmu59MHHHDzWlQmnHw6egmOEQKqkDs/u0DtbhkOl g96I7GCQw1tV/xndkwbg2Wo23woYcQX/7zDbK0= X-Received: by 2002:a05:620a:4622:b0:8cf:f5b3:b878 with SMTP id af79cd13be357-8ddcf1b8347mr216319085a.36.1775792496039; Thu, 09 Apr 2026 20:41:36 -0700 (PDT) Received: from TDC4045031631.e0cglfehwr0e5gttmepj3hi3hf.ux.internal.cloudapp.net ([20.63.37.123]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8ddb9351afasm109911785a.36.2026.04.09.20.41.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Apr 2026 20:41:35 -0700 (PDT) From: Ashutosh Desai To: dri-devel@lists.freedesktop.org Cc: maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, linux-kernel@vger.kernel.org, Ashutosh Desai Subject: [PATCH] drm/dp/mst: fix OOB reads in remote DPCD/I2C sideband reply parsers Date: Fri, 10 Apr 2026 03:41:23 +0000 Message-Id: <20260410034123.2433769-1-ashutoshdesai993@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 <=3D 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 and also lacked the post-increment idx bounds check (noted with a /* TODO check */ comment since the code was introduced). Add the missing bounds checks in both functions, consistent with the pattern used throughout the rest of the sideband parser. Signed-off-by: Ashutosh Desai --- drivers/gpu/drm/display/drm_dp_mst_topology.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/dr= m/display/drm_dp_mst_topology.c index 170113520..9cef6c576 100644 --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c @@ -873,6 +873,8 @@ static bool drm_dp_sideband_parse_remote_dpcd_read(stru= ct drm_dp_sideband_msg_rx idx++; if (idx > raw->curlen) goto fail_len; + if (idx + repmsg->u.remote_dpcd_read_ack.num_bytes > raw->curlen) + goto fail_len; =20 memcpy(repmsg->u.remote_dpcd_read_ack.bytes, &raw->msg[idx], repmsg->u.re= mote_dpcd_read_ack.num_bytes); return true; @@ -907,7 +909,11 @@ 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 =3D raw->msg[idx]; idx++; - /* TODO check */ + if (idx > raw->curlen) + goto fail_len; + 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.rem= ote_i2c_read_ack.num_bytes); return true; fail_len: --=20 2.34.1