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Subject: Re: [PATCH v2] net: bridge: Fix a warning when del bridge sysfs
To:     Wang Hai <wanghai38@huawei.com>, <kuba@kernel.org>,
        <davem@davemloft.net>, <roopa@nvidia.com>
CC:     <bridge@lists.linux-foundation.org>, <netdev@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
References: <20201211122921.40386-1-wanghai38@huawei.com>
From:   Nikolay Aleksandrov <nikolay@nvidia.com>
Message-ID: <ca27bd77-a679-b410-386e-f7cbd4fe1960@nvidia.com>
Date:   Fri, 11 Dec 2020 14:34:31 +0200
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On 11/12/2020 14:29, Wang Hai wrote:
> I got a warining report:
> 
> br_sysfs_addbr: can't create group bridge4/bridge
> ------------[ cut here ]------------
> sysfs group 'bridge' not found for kobject 'bridge4'
> WARNING: CPU: 2 PID: 9004 at fs/sysfs/group.c:279 sysfs_remove_group fs/sysfs/group.c:279 [inline]
> WARNING: CPU: 2 PID: 9004 at fs/sysfs/group.c:279 sysfs_remove_group+0x153/0x1b0 fs/sysfs/group.c:270
> Modules linked in: iptable_nat
> ...
> Call Trace:
>   br_dev_delete+0x112/0x190 net/bridge/br_if.c:384
>   br_dev_newlink net/bridge/br_netlink.c:1381 [inline]
>   br_dev_newlink+0xdb/0x100 net/bridge/br_netlink.c:1362
>   __rtnl_newlink+0xe11/0x13f0 net/core/rtnetlink.c:3441
>   rtnl_newlink+0x64/0xa0 net/core/rtnetlink.c:3500
>   rtnetlink_rcv_msg+0x385/0x980 net/core/rtnetlink.c:5562
>   netlink_rcv_skb+0x134/0x3d0 net/netlink/af_netlink.c:2494
>   netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
>   netlink_unicast+0x4a0/0x6a0 net/netlink/af_netlink.c:1330
>   netlink_sendmsg+0x793/0xc80 net/netlink/af_netlink.c:1919
>   sock_sendmsg_nosec net/socket.c:651 [inline]
>   sock_sendmsg+0x139/0x170 net/socket.c:671
>   ____sys_sendmsg+0x658/0x7d0 net/socket.c:2353
>   ___sys_sendmsg+0xf8/0x170 net/socket.c:2407
>   __sys_sendmsg+0xd3/0x190 net/socket.c:2440
>   do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
>   entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> In br_device_event(), if the bridge sysfs fails to be added,
> br_device_event() should return error. This can prevent warining
> when removing bridge sysfs that do not exist.
> 
> Fixes: bb900b27a2f4 ("bridge: allow creating bridge devices with netlink")
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Signed-off-by: Wang Hai <wanghai38@huawei.com>
> ---
> v1->v2: Fix this by check br_sysfs_addbr() return value as Nik's suggestion
>  net/bridge/br.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/net/bridge/br.c b/net/bridge/br.c
> index 401eeb9142eb..1b169f8e7491 100644
> --- a/net/bridge/br.c
> +++ b/net/bridge/br.c
> @@ -43,7 +43,10 @@ static int br_device_event(struct notifier_block *unused, unsigned long event, v
>  
>  		if (event == NETDEV_REGISTER) {
>  			/* register of bridge completed, add sysfs entries */
> -			br_sysfs_addbr(dev);
> +			err = br_sysfs_addbr(dev);
> +			if (err)
> +				return notifier_from_errno(err);
> +
>  			return NOTIFY_DONE;
>  		}
>  	}
> 

Patch looks good, I also tested it with a notifier error injecting.
Tested-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>