[PATCH 4.20 38/80] CIFS: fix use-after-free of the lease keys

Greg Kroah-Hartman
2019-02-04T10:52:58Z

From: Aurelien Aptel <aaptel@suse.com>

commit d339adc12a4f885b572c5412e4869af8939db854 upstream.

The request buffers are freed right before copying the pointers.
Use the func args instead which are identical and still valid.

Simple reproducer (requires KASAN enabled) on a cifs mount:

echo foo > foo ; tail -f foo & rm foo

Cc: <stable@vger.kernel.org> # 4.20
Fixes: 179e44d49c2f ("smb3: add tracepoint for sending lease break responses to server")
Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Paulo Alcantara <palcantara@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/cifs/smb2pdu.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -4339,8 +4339,8 @@ SMB2_lease_break(const unsigned int xid,
rc = cifs_send_recv(xid, ses, &rqst, &resp_buf_type, flags, &rsp_iov);
cifs_small_buf_release(req);

- please_key_low = (__u64 *)req->LeaseKey;
- please_key_high = (__u64 *)(req->LeaseKey+8);
+ please_key_low = (__u64 *)lease_key;
+ please_key_high = (__u64 *)(lease_key+8);
if (rc) {
cifs_stats_fail_inc(tcon, SMB2_OPLOCK_BREAK_HE);
trace_smb3_lease_err(le32_to_cpu(lease_state), tcon->tid,