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 417BB3C1D70; Thu, 30 Jul 2026 15:32:26 +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=1785425547; cv=none; b=mjoVRbjU9Tc0OkwkGzx59CRZT+g7qDkpdxpxITAaU08RsyEgEqH0rQKLpiLltqFjrY8UHMrU9jmOU6yjMS2n3vCrqvv0ek7uGSWKGBW7pWbf4DBBZkRO0EbckOcb4PrVOeo9HvMW5AZ/nrQiJWLMS/LLjjuHuWXQdkN1bv5Tx1k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785425547; c=relaxed/simple; bh=qq6xq8WNhD2woY5ikldvD4rH6SSdXJp8VOgRSc0BnII=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pp8qInkUHBOvG+2rO4j6HFKoOKUblS3Azgivb5QBuR0pnQI3oQO6QmU28PkeXw875qwOSt20yfJRoyJPjIxgUYpCJumtYt/ulmBH8Uaf3Wv2GV71irZI7OHntjy0W+GmbunPC4+kUtQFyCUKFTprSxAl0k00fOWx6aT8YIlOZnI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=X6avKSdh; 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="X6avKSdh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9A80B1F000E9; Thu, 30 Jul 2026 15:32:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785425546; bh=M7LLQgjGodZD5ujaufUOq4UatO2nJijA7d6buecM8dk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=X6avKSdhgsc0BUoQZFulkcu8ljuEPFizkjF9mqjcj6J2BTUJKqm6mFciJPpaEBxrH nBa13eWkPT1Q07wS6a+tNLFa8ddq5pRzerS7qA6lhf1nTOtBxqUZGxrL9AZNgYHk2D tpHrtaxnROHhJwlRKBmNHaz8m2g0EQLyGqaHuMV0= 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 6.12 108/602] ksmbd: validate compound request size before reading StructureSize2 Date: Thu, 30 Jul 2026 16:08:20 +0200 Message-ID: <20260730141438.260647574@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141435.976815864@linuxfoundation.org> References: <20260730141435.976815864@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 6.12-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 ae501024665e1f..6317edbfe4fa43 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