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CIFS: fix use-after-free of the lease keys 

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: 179e44d49c ("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>
This commit is contained in:
Aurelien Aptel 2019-01-31 13:46:07 +01:00 committed by Steve French
parent 082aaa8700
commit d339adc12a
1 changed files with 2 additions and 2 deletions
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4
fs/cifs/smb2pdu.c
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@ -4441,8 +4441,8 @@ SMB2_lease_break(const unsigned int xid, struct cifs_tcon *tcon,
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,