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 8B415442FBC; Thu, 30 Jul 2026 15:03:30 +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=1785423811; cv=none; b=oU5BR+aW1jankqntdxx7SnoGUh0lxH4orNA3dLqKlRRhrr1EYXmUcX7Tpt8wzZbomYKErDFzTWfq7prP10PZCUGknVxszXIDQdf8xpas7mJTXh26nHufZqh6Lvo8iPM+QVrbMCa+wouoVrJl6LR2AA0y7v6XUu2yDZ+3al8DAck= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785423811; c=relaxed/simple; bh=kCMof6L7T5br+iDTUrgNDlSEp8BZFctv5omtyGnsoHg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mxyFgrKgqAjVRfzareR/mwbOJx2QuT4AbhqgWCgDbQDhcqbk5DctYTCrByGCTJz7C3BajIKBFFMIUn2uEyf9pV/Vj+1PiRP0daCtbk8jtby/puWtn3evqVElquJBSVOeYZuKG6ju0D0fEuEaYQSzX1q/2E0HFAttKhwBJhvJSfQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=cjNS1TB4; 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="cjNS1TB4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E5FF91F01562; Thu, 30 Jul 2026 15:03:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785423810; bh=LcZQms3uZoLWdw27tZHdnIvpHxmoNY3WOTiUs0Fr2FQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=cjNS1TB4RfpyuZRIn6iI345yFqwqt161lSheOGZhvJUx+3ca96fiLZkIzoG+vtcUc LTslz7Z68m8iW3B4x0zWXJiltv5ccC9SEqrUm8OLss4cELGHFKBnNzvCE4Q/LdBOK5 8XAs95fdPzJjnSlGZNx8I6qbSlIQLcCrMNBIybag= 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 6.18 130/675] ksmbd: validate compound request size before reading StructureSize2 Date: Thu, 30 Jul 2026 16:07:40 +0200 Message-ID: <20260730141447.907582470@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141445.110192266@linuxfoundation.org> References: <20260730141445.110192266@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 6.18-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 67a2d7a793f6ed..b11d854d3fcfba 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