netdev - Re: [PATCH net-next] ipv6: also use netdev_hold() in ip6_route_check

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Message-ID: <1a575a29-ed2c-a6c1-24c0-95e4f10db757@kernel.org>
Date: Fri, 16 Jun 2023 17:20:12 -0700
From: David Ahern <dsahern@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>, "David S . Miller"
 <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com,
 syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH net-next] ipv6: also use netdev_hold() in
 ip6_route_check_nh()

On 6/16/23 2:57 AM, Eric Dumazet wrote:
> In blamed commit, we missed the fact that ip6_validate_gw()
> could change dev under us from ip6_route_check_nh()

I guess I should have caught up on all email before responding to your
last one. I read "change dev" as changing it from say eth0 to eth1 but
you mean can change the value by actually setting it.

> 
> In this fix, I use GFP_ATOMIC in order to not pass too many additional
> arguments to ip6_validate_gw() and ip6_route_check_nh() only
> for a rarely used debug feature.
> 

...

> 
> Fixes: 70f7457ad6d6 ("net: create device lookup API with reference tracking")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: David Ahern <dsahern@...nel.org>
> ---
>  net/ipv6/route.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 

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