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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Dan Carpenter <dan.carpenter@oracle.com>,
        Steven French <Steven.French@microsoft.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL 3.18 11/13] cifs: read overflow in
 is_valid_oplock_break()
Thread-Topic: [PATCH AUTOSEL 3.18 11/13] cifs: read overflow in
 is_valid_oplock_break()
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Date:   Mon, 1 Oct 2018 00:41:52 +0000
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From: Dan Carpenter <dan.carpenter@oracle.com>

[ Upstream commit 097f5863b1a0c9901f180bbd56ae7d630655faaa ]

We need to verify that the "data_offset" is within bounds.

Reported-by: Dr Silvio Cesare of InfoSect <silvio.cesare@gmail.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 fs/cifs/misc.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
index eedbc34e19db..c8662e212afc 100644
--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -405,9 +405,17 @@ is_valid_oplock_break(char *buffer, struct TCP_Server_=
Info *srv)
 			(struct smb_com_transaction_change_notify_rsp *)buf;
 		struct file_notify_information *pnotify;
 		__u32 data_offset =3D 0;
+		size_t len =3D srv->total_read - sizeof(pSMBr->hdr.smb_buf_length);
+
 		if (get_bcc(buf) > sizeof(struct file_notify_information)) {
 			data_offset =3D le32_to_cpu(pSMBr->DataOffset);
=20
+			if (data_offset >
+			    len - sizeof(struct file_notify_information)) {
+				cifs_dbg(FYI, "invalid data_offset %u\n",
+					 data_offset);
+				return true;
+			}
 			pnotify =3D (struct file_notify_information *)
 				((char *)&pSMBr->hdr.Protocol + data_offset);
 			cifs_dbg(FYI, "dnotify on %s Action: 0x%x\n",
--=20
2.17.1