linux-kernel - [PATCH 4.19 29/96] cifs: Fix use-after-free in SMB2

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Date:   Wed, 24 Apr 2019 19:09:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, ZhangXiaoxu <zhangxiaoxu5@...wei.com>,
        Steve French <stfrench@...rosoft.com>,
        Pavel Shilovsky <pshilov@...rosoft.com>
Subject: [PATCH 4.19 29/96] cifs: Fix use-after-free in SMB2_write

From: ZhangXiaoxu <zhangxiaoxu5@...wei.com>

commit 6a3eb3360667170988f8a6477f6686242061488a upstream.

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@...wei.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
CC: Stable <stable@...r.kernel.org> 4.18+
Reviewed-by: Pavel Shilovsky <pshilov@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/cifs/smb2pdu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -3591,7 +3591,6 @@ SMB2_write(const unsigned int xid, struc
 
 	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) {
@@ -3609,6 +3608,7 @@ SMB2_write(const unsigned int xid, struc
 				     io_parms->offset, *nbytes);
 	}
 
+	cifs_small_buf_release(req);
 	free_rsp_buf(resp_buftype, rsp);
 	return rc;
 }