linux-kernel - [PATCH AUTOSEL 5.6 040/606] cifs: fix leaked reference on requeued write

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Message-Id: <20200608231211.3363633-40-sashal@kernel.org>
Date:   Mon,  8 Jun 2020 19:02:45 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Adam McCoy <adam@...sedomani.com>,
        Steve French <stfrench@...rosoft.com>,
        Pavel Shilovsky <pshilov@...rosoft.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org
Subject: [PATCH AUTOSEL 5.6 040/606] cifs: fix leaked reference on requeued write

From: Adam McCoy <adam@...sedomani.com>

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@...sedomani.com>
Signed-off-by: Steve French <stfrench@...rosoft.com>
CC: Stable <stable@...r.kernel.org>
Reviewed-by: Pavel Shilovsky <pshilov@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/cifs/cifssmb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 6f6fb3606a5d..a4545aa04efc 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -2138,8 +2138,8 @@ cifs_writev_requeue(struct cifs_writedata *wdata)
 			}
 		}
 
+		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;
-- 
2.25.1