[PATCH 4.19 62/80] cifs: fix leaked reference on requeued write

From: Greg Kroah-Hartman
Date: Mon May 18 2020 - 14:20:36 EST


From: Adam McCoy <adam@xxxxxxxxxxxxxxx>

commit a48137996063d22ffba77e077425f49873856ca5 upstream.

Failed async writes that are requeued may not clean up a refcount
on the file, which can result in a leaked open. This scenario arises
very reliably when using persistent handles and a reconnect occurs
while writing.

cifs_writev_requeue only releases the reference if the write fails
(rc != 0). The server->ops->async_writev operation will take its own
reference, so the initial reference can always be released.

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

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

--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -2051,8 +2051,8 @@ cifs_writev_requeue(struct cifs_writedat
}
}

+ kref_put(&wdata2->refcount, cifs_writedata_release);
if (rc) {
- kref_put(&wdata2->refcount, cifs_writedata_release);
if (is_retryable_error(rc))
continue;
i += nr_pages;