From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-qv1-f42.google.com (mail-qv1-f42.google.com [209.85.219.42]) (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 9611943F4BC for ; Tue, 7 Jul 2026 18:06:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.42 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783447577; cv=none; b=Thwu9N0rggc7c5VbbBAqV42PfAslMLRKrCgNNOpD9q+rM1tjq+X+IGV3QDxMtIvAbDAoOOesjUnK3PuzQq4kiTGAaa8pskaMuKS4kocNu+F0wVKsx6yhTBF9GAAeGNRAZtP+0JCE8hM6/ReapHwKbTq3xJNPvUzBvPfCz48VGt8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783447577; c=relaxed/simple; bh=jN7ul/UghLLZ/zGDRaDzZiy3k7fJlhFzSW7xay+Y8qo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HvCBHwZbptnwCp63rzntYfB7Kyj84lYQIYLL1tERCDxecHfSU7v1hJvYpxdvUVM2tBCzNI2+LO4tvBtSVDA3B/4nvdeRNeUCrfe+G3Yk20Z5kxYUxS0YUwbCmcVFv0Q1fmDFTPl38EYfzAvpVBjDePeeHIWLENNXAvbR4CJMzyo= 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=OmOdYe9M; arc=none smtp.client-ip=209.85.219.42 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="OmOdYe9M" Received: by mail-qv1-f42.google.com with SMTP id 6a1803df08f44-8f032b47e3cso28246746d6.0 for ; Tue, 07 Jul 2026 11:06:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1783447574; x=1784052374; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=pibmK0IsgRE7prkfqOsLJI7ZN6aYkjpZU+5r5feOTgk=; b=OmOdYe9Mhcn+6Vt59o25z7HJl2+60fTH+KMfoukXUfJWIYvswE/cX/DMjPCxn963n1 WAnujroRQhppwJxdGFy8gMZnRNVKkIW+G9khBgpx+E3ViIseBCHS+p2Tm7Qw2wE+zIos b0cVJV3FviH+XjW/wXjqNb+tO64rDyJBaxrSMndrQnfGxGfwOPJLGiidhlmIfbgmtgZn cbcOkdksijyjCzinlhGoRJct1CfJGmikwxwFBEW0gbzVwULQH1IPxHp+dYwPExNlKfy0 +4tPPTkIEC20VD5VhBuQEY5Y/v6BZZj4nx5tB5q3zglk8En1147mMb+BCHg24hkaalLG 3INg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1783447574; x=1784052374; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=pibmK0IsgRE7prkfqOsLJI7ZN6aYkjpZU+5r5feOTgk=; b=e0jiZFUYjSHggmh621IPB4Ami+BsK7WiHzgLCgHFUl9R9IZAgND+F4NBEpCHJL1OCj rhRyJ/C4ZcckX0nLl4DpONMHbDxuyxcBQBHtkCVW3ZzkW9zlI5FZ3aIWGa3gJEvzZjX8 gsM31FLwjUlidbldm5XxSaodwd7Olxg1OiAABHzL9ePVyLL3Hg8TP4mibJRaTZyWXArr J+5x0U24HSQ4nO94PHsa3VHfHfEA0X6R3KFD9Del9EL6ak+S7G31wjXfVWVW3DBwlvgq A6bRfKT2g0FNn+fHA+Mn3Wq+K0av5o2svuocgXQ6weHF4xDmE/IVviK2x+ZrgOUAfuMF P5ug== X-Forwarded-Encrypted: i=1; AHgh+RpVuQOl3+TITkRwVXEpPtVA1QSvTP2qr6XjlzecxXEWXfrQPcjH/EnOxWECtnv463QHWY9RoBRoI6f3qV0=@vger.kernel.org X-Gm-Message-State: AOJu0YyR7snly2VkKAid8ll7RMD3Sac1M12Gu/xpI2ZxXW/KDfm4g0dU fxB3I1XWWEt8fDqpAgB+QGls4XuNU8njORv5Zazf/KIMBoKcVtB9P1x5 X-Gm-Gg: AfdE7cmOW6tT3kcjVgNmkx/xm2SjR7nkKfEcyT+ESvqjkxtHoQbShqS90UEvGCgPWbT vVxTM88MgokQTNjTV2RVnVw5wSbJQ1ONK80hCYzYqSm/mVuKTmDeNJ+/1wBk7HjrMXyP9wcIkw4 QiYC+DQTquiz1XZuGe4+c8yjjREHIGLPzbHC3UneaDFDrk530Lvz3QObQ+uQHpBFxayl39QxlI5 iTwAHvxxXbzg3lKKQhwZDFo2DvUpulg0wJKd0jOEC0smkuPxjd77VOSYBEmrbpoWzEp9cfVwcu1 kkxLqGOC8rM6ClDvAfaEefPDof4trPAB4Ev08DTd/TgQVmbfb/1A7bG4SwXfQTsp1krk1mNmY/J IbydyJmbYizB2btGbFQ6oGQMzwnuDiCCGq3hnuiqMyw/0BsH4RJguja97le2OpJ0XB46VsAYqg0 Ljamw547ZLzNSFe2qKSB3HdZ2Lw7aMigLq3nFv2jtz2qWxfEJS5URomjnERn08to3GXHve95/Mo Tnr4oEOVIwUkJYI34d0srLJ77gfufVe X-Received: by 2002:a05:6214:5005:b0:8f1:3533:7a83 with SMTP id 6a1803df08f44-8fcb47118edmr73327336d6.33.1783447574212; Tue, 07 Jul 2026 11:06:14 -0700 (PDT) Received: from server0.tail6e7dd.ts.net (c-68-48-65-54.hsd1.mi.comcast.net. [68.48.65.54]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8f471de87e3sm166404376d6.35.2026.07.07.11.06.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2026 11:06:13 -0700 (PDT) From: Michael Bommarito To: Ilya Dryomov , Alex Markuze , Viacheslav Dubeyko Cc: ceph-devel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 3/4] ceph: bound num_export_targets array for mds info v2/v3 Date: Tue, 7 Jul 2026 14:05:59 -0400 Message-ID: <4a7bd76ba2a82496e6076cc43a73bb3ff3847720.1783447231.git.michael.bommarito@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7bit ceph_mdsmap_decode() in fs/ceph/mdsmap.c reads num_export_targets from each per-mds info record and advances the decode cursor by num_export_targets * sizeof(u32) without first checking that many bytes remain. The only upper-bound check that catches a runaway cursor (*p > info_end) is gated on info_v >= 4, because info_end is left NULL for info_v 2 and 3. When the monitor sends an MDS map whose per-mds info version is 2 or 3 with an oversized num_export_targets, the cursor moves past the message front buffer and the later export-targets loop calls the unchecked ceph_decode_32() on out-of-bounds memory. A kernel client processes CEPH_MSG_MDS_MAP from its monitor session (net/ceph/mon_client.c dispatches it; fs/ceph/super.c routes it to ceph_mdsc_handle_mdsmap(), which sets end to the front buffer bound and calls ceph_mdsmap_decode()). A malicious or compromised monitor, or an on-path attacker on an unsigned/unencrypted messenger session, can therefore drive an out-of-bounds read in the client kernel; on x86_64 with KASAN it is reported as a slab-out-of-bounds read in ceph_mdsmap_decode(). The decoded values land in the internal info->export_targets[] array, so the consequence is a kernel out-of-bounds read, not an information leak to the attacker. Impact: a malicious or compromised Ceph monitor sending an MDS map with a per-mds info version of 2 or 3 and an oversized num_export_targets field triggers an out-of-bounds read in the CephFS client kernel. Add a ceph_decode_need() for the export-targets array before advancing the cursor, so the bound is enforced for every info_v >= 2, not only info_v >= 4. This mirrors the count-then-need idiom already used for m_data_pg_pools later in the same function. Compute the export-targets byte count with size_mul() and reuse that checked length when advancing the cursor, so the attacker-controlled num_export_targets multiplication fails closed on overflow rather than relying on the later kcalloc() guard. Fixes: d463a43d69f4 ("ceph: CEPH_FEATURE_MDSENC support") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Michael Bommarito Reviewed-by: Viacheslav Dubeyko --- fs/ceph/mdsmap.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/ceph/mdsmap.c b/fs/ceph/mdsmap.c index d8e46eb7e5eb5..c0f63f0460f67 100644 --- a/fs/ceph/mdsmap.c +++ b/fs/ceph/mdsmap.c @@ -3,6 +3,7 @@ #include #include +#include #include #include #include @@ -126,6 +127,7 @@ struct ceph_mdsmap *ceph_mdsmap_decode(struct ceph_mds_client *mdsc, void **p, u8 mdsmap_v; u16 mdsmap_ev; u32 target; + size_t export_targets_len; m = kzalloc_obj(*m, GFP_NOFS); if (!m) @@ -224,8 +226,11 @@ struct ceph_mdsmap *ceph_mdsmap_decode(struct ceph_mds_client *mdsc, void **p, *p += namelen; if (info_v >= 2) { ceph_decode_32_safe(p, end, num_export_targets, bad); + export_targets_len = size_mul(num_export_targets, + sizeof(u32)); + ceph_decode_need(p, end, export_targets_len, bad); pexport_targets = *p; - *p += num_export_targets * sizeof(u32); + *p += export_targets_len; } else { num_export_targets = 0; } -- 2.53.0