linux-kernel - [PATCH] net/sunrpc: fix potential memory leaks in rpc_sysfs_xprt_state

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Date:   Wed, 10 Aug 2022 23:29:13 +0800
From:   Xin Xiong <xiongx18@...an.edu.cn>
To:     Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        Jeff Layton <jlayton@...nel.org>,
        “David S . Miller  
        <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Olga Kornievskaia <kolga@...app.com>,
        linux-nfs@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     yuanxzhang@...an.edu.cn, Xin Xiong <xiongx18@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>
Subject: [PATCH] net/sunrpc: fix potential memory leaks in rpc_sysfs_xprt_state_change()

The issue happens on some error handling paths. When the function
fails to grab the object `xprt`, it simply returns 0, forgetting to
decrease the reference count of another object `xps`, which is
increased by rpc_sysfs_xprt_kobj_get_xprt_switch(), causing refcount
leaks. Also, the function forgets to check whether `xps` is valid
before using it, which may result in NULL-dereferencing issues.

Fix it by adding proper error handling code when either `xprt` or
`xps` is NULL.

Fixes: 5b7eb78486cd ("SUNRPC: take a xprt offline using sysfs")
Signed-off-by: Xin Xiong <xiongx18@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
---
 net/sunrpc/sysfs.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/sunrpc/sysfs.c b/net/sunrpc/sysfs.c
index a3a2f8aeb80e..d1a15c6d3fd9 100644
--- a/net/sunrpc/sysfs.c
+++ b/net/sunrpc/sysfs.c
@@ -291,8 +291,10 @@ static ssize_t rpc_sysfs_xprt_state_change(struct kobject *kobj,
 	int offline = 0, online = 0, remove = 0;
 	struct rpc_xprt_switch *xps = rpc_sysfs_xprt_kobj_get_xprt_switch(kobj);
 
-	if (!xprt)
-		return 0;
+	if (!xprt || !xps) {
+		count = 0;
+		goto out_put;
+	}
 
 	if (!strncmp(buf, "offline", 7))
 		offline = 1;
-- 
2.25.1