From: Ido Schimmel <idosch@idosch.org>
To: Wei Wang <weiwan@google.com>
Cc: "David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
netdev@vger.kernel.org, syzbot <syzkaller@googlegroups.com>,
David Ahern <dsahern@kernel.org>, Petr Machata <petrm@nvidia.com>,
Eric Dumazet <edumazet@google.com>
Subject: Re: [PATCH net v2] ipv6: fix suspecious RCU usage warning
Date: Wed, 10 Mar 2021 11:54:47 +0200 [thread overview]
Message-ID: <YEiXZ2K7GTVNE9F0@shredder.lan> (raw)
In-Reply-To: <20210310022035.2908294-1-weiwan@google.com>
On Tue, Mar 09, 2021 at 06:20:35PM -0800, Wei Wang wrote:
> Syzbot reported the suspecious RCU usage in nexthop_fib6_nh() when
> called from ipv6_route_seq_show(). The reason is ipv6_route_seq_start()
> calls rcu_read_lock_bh(), while nexthop_fib6_nh() calls
> rcu_dereference_rtnl().
> The fix proposed is to add a variant of nexthop_fib6_nh() to use
> rcu_dereference_bh_rtnl() for ipv6_route_seq_show().
>
> The reported trace is as follows:
> ./include/net/nexthop.h:416 suspicious rcu_dereference_check() usage!
>
> other info that might help us debug this:
>
> rcu_scheduler_active = 2, debug_locks = 1
> 2 locks held by syz-executor.0/17895:
> at: seq_read+0x71/0x12a0 fs/seq_file.c:169
> at: seq_file_net include/linux/seq_file_net.h:19 [inline]
> at: ipv6_route_seq_start+0xaf/0x300 net/ipv6/ip6_fib.c:2616
[...]
>
> Fixes: f88d8ea67fbdb ("ipv6: Plumb support for nexthop object in a fib6_info")
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Signed-off-by: Wei Wang <weiwan@google.com>
> Cc: David Ahern <dsahern@kernel.org>
> Cc: Ido Schimmel <idosch@idosch.org>
> Cc: Petr Machata <petrm@nvidia.com>
> Cc: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
next prev parent reply other threads:[~2021-03-10 9:55 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-10 2:20 [PATCH net v2] ipv6: fix suspecious RCU usage warning Wei Wang
2021-03-10 9:54 ` Ido Schimmel [this message]
2021-03-10 16:15 ` David Ahern
2021-03-10 20:50 ` patchwork-bot+netdevbpf
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