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 A437F3C3F4C; Thu, 30 Jul 2026 16:02:17 +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=1785427338; cv=none; b=PKfHo0etksWYcpQMolVokCKg/qWpWqfSYvnr/tVcoSNefb7w1d1Ca1VIw2Kzs/doGkfcLrcQAf3WB7qKmhI+S0i4Q5Fu+zI6zFCRETCCJkHq4ghSgh0WMcOHTHbN+n2meOxjHsfJiSDByyBoyWJeWcaIWmMt4BV9R1OtGrPTfF0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785427338; c=relaxed/simple; bh=5DE0Ys+iTrG4Nnkrvto6llp2Vn4MA0QOMmtjRToDNpg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Jm1DtQEp86O4V4ha7BOBP/U3AEXv6nrTlslUVe4MDkS1onxmLD4Fdzy2d2WPi3SwtJ+HmeeduQRBdtS4xnbKEoiizKxryT3W9cv4uxYmUKyT25xmvFhkhz6000Q/UcTQoRy0Yibrw9vwmGpIBZKbVWQ82CgUKKy/JqvEoylAhmk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=UvcXT8w9; 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="UvcXT8w9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0AA721F000E9; Thu, 30 Jul 2026 16:02:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785427337; bh=LswwvPz1oATjhB84++iy20lEVwkkXGCc+GNZysjto2Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=UvcXT8w9ryCUNH+sRW3QiTfIY3boY+9pSa/NhU+wkInmxfNJu22nuqMpiNLSz6ADR 0IWDyxVM+dLTancAdHU1mojkdPCR1EaQtCgymf3RqPL+ebzhw+r9FrKmoFVfeoNohe 2E8ByLHq9Iaa6d7pc6QKpfZ95F4c+Cqm2UEIs/JI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, AutonomousCodeSecurity@microsoft.com, "Xiang Mei (Microsoft)" , Namjae Jeon , Steve French , Sasha Levin Subject: [PATCH 6.6 091/484] ksmbd: validate compound request size before reading StructureSize2 Date: Thu, 30 Jul 2026 16:09:48 +0200 Message-ID: <20260730141425.425436214@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141423.392222816@linuxfoundation.org> References: <20260730141423.392222816@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 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Xiang Mei (Microsoft) [ Upstream commit 15b38176fd1530372905c602fde51fe89ec8c877 ] When ksmbd validates a compound (chained) SMB2 request, ksmbd_smb2_check_message() reads pdu->StructureSize2 without first checking that the compound element is large enough to contain it. StructureSize2 is a 2-byte field at offset 64 (__SMB2_HEADER_STRUCTURE_SIZE) from the start of each element. The compound-walking logic only guarantees that a full 64-byte SMB2 header is present for the trailing element: when NextCommand is 0, len is reduced to the number of bytes remaining after next_smb2_rcv_hdr_off. A remote client can craft a compound request whose last element has exactly 64 bytes, so the 2-byte StructureSize2 read at offset 64 extends one byte past the receive buffer, producing a slab-out-of-bounds read. BUG: KASAN: slab-out-of-bounds in ksmbd_smb2_check_message (fs/smb/server/smb2misc.c:402) Read of size 2 at addr ffff888012ae31ac by task kworker/0:1/14 The buggy address is located 172 bytes inside of allocated 173-byte region Workqueue: ksmbd-io handle_ksmbd_work Call Trace: ... kasan_report (mm/kasan/report.c:595) ksmbd_smb2_check_message (fs/smb/server/smb2misc.c:402) handle_ksmbd_work (fs/smb/server/server.c:119) process_one_work (kernel/workqueue.c:3314) worker_thread (kernel/workqueue.c:3397) kthread (kernel/kthread.c:436) ret_from_fork (arch/x86/kernel/process.c:158) ret_from_fork_asm (arch/x86/entry/entry_64.S:245) Reject any compound element that is too small to hold StructureSize2 before dereferencing it. Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Reported-by: AutonomousCodeSecurity@microsoft.com Signed-off-by: Xiang Mei (Microsoft) Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Sasha Levin --- fs/smb/server/smb2misc.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/smb/server/smb2misc.c b/fs/smb/server/smb2misc.c index 727cb49926ee52..ffbddf00d24e95 100644 --- a/fs/smb/server/smb2misc.c +++ b/fs/smb/server/smb2misc.c @@ -400,6 +400,11 @@ int ksmbd_smb2_check_message(struct ksmbd_work *work) return 1; } + if (len < __SMB2_HEADER_STRUCTURE_SIZE + sizeof(__le16)) { + ksmbd_debug(SMB, "Message is too small for StructureSize2\n"); + return 1; + } + if (smb2_req_struct_sizes[command] != pdu->StructureSize2) { if (!(command == SMB2_OPLOCK_BREAK_HE && (le16_to_cpu(pdu->StructureSize2) == OP_BREAK_STRUCT_SIZE_20 || -- 2.53.0