[PATCH 3.16 238/328] cifs: integer overflow in in SMB2_ioctl()

Ben Hutchings
2018-12-09T22:22:38Z

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

commit 2d204ee9d671327915260071c19350d84344e096 upstream.

The "le32_to_cpu(rsp->OutputOffset) + *plen" addition can overflow and
wrap around to a smaller value which looks like it would lead to an
information leak.

Fixes: 4a72dafa19ba ("SMB2 FSCTL and IOCTL worker function")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
[bwh: Backported to 3.16: Use get_rfc1002_length(rsp) instead of
rsp->iov.iov_len]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/cifs/smb2pdu.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -1394,14 +1394,14 @@ SMB2_ioctl(const unsigned int xid, struc
/* We check for obvious errors in the output buffer length and offset */
if (*plen == 0)
goto ioctl_exit; /* server returned no data */
- else if (*plen > 0xFF00) {
+ else if (*plen > get_rfc1002_length(rsp) || *plen > 0xFF00) {
cifs_dbg(VFS, "srv returned invalid ioctl length: %d\n", *plen);
*plen = 0;
rc = -EIO;
goto ioctl_exit;
}

- if (get_rfc1002_length(rsp) < le32_to_cpu(rsp->OutputOffset) + *plen) {
+ if (get_rfc1002_length(rsp) - *plen < le32_to_cpu(rsp->OutputOffset)) {
cifs_dbg(VFS, "Malformed ioctl resp: len %d offset %d\n", *plen,
le32_to_cpu(rsp->OutputOffset));
*plen = 0;