netdev - [PATCH net v3] net: fix memory leak in register

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Message-ID: <20201201135457.3549435-1-yangyingliang@huawei.com>
Date:   Tue, 1 Dec 2020 21:54:57 +0800
From:   Yang Yingliang <yangyingliang@...wei.com>
To:     <netdev@...r.kernel.org>
CC:     <davem@...emloft.net>, <kuba@...nel.org>,
        <toshiaki.makita1@...il.com>, <rkovhaev@...il.com>,
        <stephen@...workplumber.org>, <Jason@...c4.com>,
        <yangyingliang@...wei.com>
Subject: [PATCH net v3] net: fix memory leak in register_netdevice() on error path

I got a memleak report when doing fault-inject test:

unreferenced object 0xffff88810ace9000 (size 1024):
  comm "ip", pid 4622, jiffies 4295457037 (age 43.378s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<00000000008abe41>] __kmalloc+0x10f/0x210
    [<000000005d3533a6>] veth_dev_init+0x140/0x310
    [<0000000088353c64>] register_netdevice+0x496/0x7a0
    [<000000001324d322>] veth_newlink+0x40b/0x960
    [<00000000d0799866>] __rtnl_newlink+0xd8c/0x1360
    [<00000000d616040a>] rtnl_newlink+0x6b/0xa0
    [<00000000e0a1600d>] rtnetlink_rcv_msg+0x3cc/0x9e0
    [<000000009eeff98b>] netlink_rcv_skb+0x130/0x3a0
    [<00000000500f8be1>] netlink_unicast+0x4da/0x700
    [<00000000666c03b3>] netlink_sendmsg+0x7fe/0xcb0
    [<0000000073b28103>] sock_sendmsg+0x143/0x180
    [<00000000ad746a30>] ____sys_sendmsg+0x677/0x810
    [<0000000087dd98e5>] ___sys_sendmsg+0x105/0x180
    [<00000000028dd365>] __sys_sendmsg+0xf0/0x1c0
    [<00000000a6bfbae6>] do_syscall_64+0x33/0x40
    [<00000000e00521b4>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

It seems ifb and loopback may also hit the leak, so I try to fix this in
register_netdevice().

In common case, priv_destructor() will be called in netdev_run_todo()
after calling ndo_uninit() in rollback_registered(), on other error
path in register_netdevice(), ndo_uninit() and priv_destructor() are
called before register_netdevice() return, but in this case,
priv_destructor() will never be called, then it causes memory leak,
so we should call priv_destructor() here.

Reported-by: Hulk Robot <hulkci@...wei.com>
Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
---
v2 -> v3: In wireguard driver, priv_destructor() will call
free_netdev(), but it is assigned after register_netdevice(),
so it will not lead a double free, drop patch#1. Also I've
test wireguard device, it's no memory leak on this error path.
---
 net/core/dev.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 82dc6b48e45f..51b9cf1ff6a1 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10003,6 +10003,16 @@ int register_netdevice(struct net_device *dev)
 		rcu_barrier();
 
 		dev->reg_state = NETREG_UNREGISTERED;
+		/* In common case, priv_destructor() will be
+		 * called in netdev_run_todo() after calling
+		 * ndo_uninit() in rollback_registered().
+		 * But in this case, priv_destructor() will
+		 * never be called, then it causes memory
+		 * leak, so we should call priv_destructor()
+		 * here.
+		 */
+		if (dev->priv_destructor)
+			dev->priv_destructor(dev);
 		/* We should put the kobject that hold in
 		 * netdev_unregister_kobject(), otherwise
 		 * the net device cannot be freed when
-- 
2.25.1