[PATCH v2 1/2] cifs: Fix use-after-free in SMB2_write

[ZhangXiaoxu <zhangxiaoxu5@huawei.com>]

There is a KASAN use-after-free:
BUG: KASAN: use-after-free in SMB2_write+0x1342/0x1580
Read of size 8 at addr ffff8880b6a8e450 by task ln/4196

Should not release the 'req' because it will use in the trace.

Fixes: eccb4422cf97(smb3: Add ftrace tracepoints for improved SMB3 debugging)

Signed-off-by: ZhangXiaoxu <zhangxiaoxu5@huawei.com>
---
 fs/cifs/smb2pdu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 21ac19f..6cf4e88 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -3752,7 +3752,6 @@ SMB2_write(const unsigned int xid, struct cifs_io_parms *io_parms,
 
 	rc = cifs_send_recv(xid, io_parms->tcon->ses, &rqst,
 			    &resp_buftype, flags, &rsp_iov);
-	cifs_small_buf_release(req);
 	rsp = (struct smb2_write_rsp *)rsp_iov.iov_base;
 
 	if (rc) {
@@ -3770,6 +3769,7 @@ SMB2_write(const unsigned int xid, struct cifs_io_parms *io_parms,
 				     io_parms->offset, *nbytes);
 	}
 
+	cifs_small_buf_release(req);
 	free_rsp_buf(resp_buftype, rsp);
 	return rc;
 }
-- 
2.7.4