netdev - Re: [PATCH net v2] ipv6: fix suspecious RCU usage warning

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Message-ID: <2cdaaaed-7529-48cf-5bcc-59da5c93c6d2@gmail.com>
Date:   Wed, 10 Mar 2021 09:15:03 -0700
From:   David Ahern <dsahern@...il.com>
To:     Wei Wang <weiwan@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Cc:     syzbot <syzkaller@...glegroups.com>,
        David Ahern <dsahern@...nel.org>,
        Ido Schimmel <idosch@...sch.org>,
        Petr Machata <petrm@...dia.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net v2] ipv6: fix suspecious RCU usage warning

On 3/9/21 7:20 PM, 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().
> 

...

> 
> Fixes: f88d8ea67fbdb ("ipv6: Plumb support for nexthop object in a fib6_info")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Wei Wang <weiwan@...gle.com>
> Cc: David Ahern <dsahern@...nel.org>
> Cc: Ido Schimmel <idosch@...sch.org>
> Cc: Petr Machata <petrm@...dia.com>
> Cc: Eric Dumazet <edumazet@...gle.com>
> ---
>  include/net/nexthop.h | 24 ++++++++++++++++++++++++
>  net/ipv6/ip6_fib.c    |  2 +-
>  2 files changed, 25 insertions(+), 1 deletion(-)
> 


Reviewed-by: David Ahern <dsahern@...nel.org>

Thanks, Wei.