netdev - Re: [PATCH net] rtnetlink: fix rtnl_dump

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Message-ID: <20241121213256.35057-1-kuniyu@amazon.com>
Date: Thu, 21 Nov 2024 13:32:56 -0800
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <edumazet@...gle.com>
CC: <davem@...emloft.net>, <eric.dumazet@...il.com>, <kuba@...nel.org>,
	<kuniyu@...zon.com>, <netdev@...r.kernel.org>, <pabeni@...hat.com>,
	<syzkaller@...glegroups.com>
Subject: Re: [PATCH net] rtnetlink: fix rtnl_dump_ifinfo() error path

From: Eric Dumazet <edumazet@...gle.com>
Date: Thu, 21 Nov 2024 19:41:05 +0000
> syzbot found that rtnl_dump_ifinfo() could return with a lock held [1]
> 
> Move code around so that rtnl_link_ops_put() and put_net()
> can be called at the end of this function.
> 
> [1]
> WARNING: lock held when returning to user space!
> 6.12.0-rc7-syzkaller-01681-g38f83a57aa8e #0 Not tainted
> syz-executor399/5841 is leaving the kernel with locks still held!
> 1 lock held by syz-executor399/5841:
>   #0: ffffffff8f46c2a0 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
>   #0: ffffffff8f46c2a0 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
>   #0: ffffffff8f46c2a0 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x22/0x250 net/core/rtnetlink.c:555
> 
> Fixes: 43c7ce69d28e ("rtnetlink: Protect struct rtnl_link_ops with SRCU.")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

I missed the error paths, thanks!

Reviewed-by: Kuniyuki Iwashima <kuniyu@...zon.com>