[PATCH 5.0 047/115] cifs: Fix use-after-free in SMB2_read

[Greg Kroah-Hartman]

From: ZhangXiaoxu <zhangxiaoxu5@xxxxxxxxxx>

commit 088aaf17aa79300cab14dbee2569c58cfafd7d6e upstream.

There is a KASAN use-after-free:
BUG: KASAN: use-after-free in SMB2_read+0x1136/0x1190
Read of size 8 at addr ffff8880b4e45e50 by task ln/1009

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@xxxxxxxxxx>
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
CC: Stable <stable@xxxxxxxxxxxxxxx> 4.18+
Reviewed-by: Pavel Shilovsky <pshilov@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -3390,8 +3390,6 @@ SMB2_read(const unsigned int xid, struct
 	rqst.rq_nvec = 1;
 
 	rc = cifs_send_recv(xid, ses, &rqst, &resp_buftype, flags, &rsp_iov);
-	cifs_small_buf_release(req);
-
 	rsp = (struct smb2_read_rsp *)rsp_iov.iov_base;
 
 	if (rc) {
@@ -3410,6 +3408,8 @@ SMB2_read(const unsigned int xid, struct
 				    io_parms->tcon->tid, ses->Suid,
 				    io_parms->offset, io_parms->length);
 
+	cifs_small_buf_release(req);
+
 	*nbytes = le32_to_cpu(rsp->DataLength);
 	if ((*nbytes > CIFS_MAX_MSGSIZE) ||
 	    (*nbytes > io_parms->length)) {