linux-kernel - [PATCH 4.9 48/59] cifs: read overflow in is_valid_oplock

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Message-Id: <20181008175552.127522988@linuxfoundation.org>
Date:   Mon,  8 Oct 2018 20:31:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Dr Silvio Cesare of InfoSect <silvio.cesare@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Steve French <stfrench@...rosoft.com>,
        Aurelien Aptel <aaptel@...e.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.9 48/59] cifs: read overflow in is_valid_oplock_break()

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpenter@...cle.com>

[ Upstream commit 097f5863b1a0c9901f180bbd56ae7d630655faaa ]

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

Reported-by: Dr Silvio Cesare of InfoSect <silvio.cesare@...il.com>
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
Reviewed-by: Aurelien Aptel <aaptel@...e.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/cifs/misc.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/fs/cifs/misc.c
+++ b/fs/cifs/misc.c
@@ -406,9 +406,17 @@ is_valid_oplock_break(char *buffer, stru
 			(struct smb_com_transaction_change_notify_rsp *)buf;
 		struct file_notify_information *pnotify;
 		__u32 data_offset = 0;
+		size_t len = srv->total_read - sizeof(pSMBr->hdr.smb_buf_length);
+
 		if (get_bcc(buf) > sizeof(struct file_notify_information)) {
 			data_offset = le32_to_cpu(pSMBr->DataOffset);
 
+			if (data_offset >
+			    len - sizeof(struct file_notify_information)) {
+				cifs_dbg(FYI, "invalid data_offset %u\n",
+					 data_offset);
+				return true;
+			}
 			pnotify = (struct file_notify_information *)
 				((char *)&pSMBr->hdr.Protocol + data_offset);
 			cifs_dbg(FYI, "dnotify on %s Action: 0x%x\n",