Re: [PATCH net-next] net/ipv6: insert the fib6 gc_link of a fib6_info only if in fib6.

[Kui-Feng Lee <sinquersw@gmail.com>]

Eric Dumazet, could you help to check if the patch works from your side
with syzbot? Thanks a lot!


On 12/7/23 14:16, thinker.li@gmail.com wrote:
> From: Kui-Feng Lee <thinker.li@gmail.com>
> 
> Check f6i->fib6_node before inserting a f6i (fib6_info) to tb6_gc_hlist.
> 
> Previously, it checks only if f6i->fib6_table is not NULL, however it is
> not enough. When a f6i is removed from a fib6_table, it's fib6_table is not
> going to be reset. fib6_node is always reset when a f6i is removed from a
> fib6_table and set when a f6i is added to a fib6_table. By checking
> fib6_node, adding a f6i t0 tb6_gc_hlist only if f6i is in the table will be
> enforced.
> 
> Fixes: 3dec89b14d37 ("net/ipv6: Remove expired routes with a separated list of routes.")
> Reported-by: syzbot+c15aa445274af8674f41@syzkaller.appspotmail.com
> Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: dsahern@kernel.org
> ---
>   include/net/ip6_fib.h | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
> index 95ed495c3a40..8477c9ff67ac 100644
> --- a/include/net/ip6_fib.h
> +++ b/include/net/ip6_fib.h
> @@ -512,7 +512,10 @@ static inline void fib6_set_expires_locked(struct fib6_info *f6i,
>   
>   	tb6 = f6i->fib6_table;
>   	f6i->expires = expires;
> -	if (tb6 && !fib6_has_expires(f6i))
> +	if (tb6 &&
> +	    rcu_dereference_protected(f6i->fib6_node,
> +				      lockdep_is_held(&tb6->tb6_lock)) &&
> +	    !fib6_has_expires(f6i))
>   		hlist_add_head(&f6i->gc_link, &tb6->tb6_gc_hlist);
>   	f6i->fib6_flags |= RTF_EXPIRES;
>   }