From: Aurelien Aptel <aaptel@suse.com>
Date: Thu, 31 Jan 2019 12:46:07 +0000 (+0100)
Subject: CIFS: fix use-after-free of the lease keys
X-Git-Tag: v5.0-rc5~13^2~1
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=d339adc12a4f885b572c5412e4869af8939db854;p=linux.git

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: 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>
---

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index ef52d6642431..77b3aaa39b35 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -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,