[PATCH 5.7 083/265] cifs: Fix cached_fid refcnt leak in open_shroot

Sasha Levin
2020-06-29T22:00:09Z

From: Xiyu Yang <xiyuyang19@fudan.edu.cn>

commit 77577de64167aa0643d47ffbaacf3642632b321b upstream.

open_shroot() invokes kref_get(), which increases the refcount of the
"tcon->crfid" object. When open_shroot() returns not zero, it means the
open operation failed and close_shroot() will not be called to decrement
the refcount of the "tcon->crfid".

The reference counting issue happens in one normal path of
open_shroot(). When the cached root have been opened successfully in a
concurrent process, the function increases the refcount and jump to
"oshr_free" to return. However the current return value "rc" may not
equal to 0, thus the increased refcount will not be balanced outside the
function, causing a refcnt leak.

Fix this issue by setting the value of "rc" to 0 before jumping to
"oshr_free" label.

Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
CC: Stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/cifs/smb2ops.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index f829f4165d38c..c6a4caa7053e9 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -759,6 +759,7 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon,
/* close extra handle outside of crit sec */
SMB2_close(xid, tcon, fid.persistent_fid, fid.volatile_fid);
}
+ rc = 0;
goto oshr_free;
}

--
2.25.1