Re: [PATCH net-next] ipv6: check fn before doing FIB6_SUBTREE(fn)

[David Miller <davem@davemloft.net>]

From: Wei Wang <weiwan@google.com>
Date: Fri, 13 Oct 2017 15:01:08 -0700

> From: Wei Wang <weiwan@google.com>
> 
> In fib6_locate(), we need to first make sure fn is not NULL before doing
> FIB6_SUBTREE(fn) to avoid crash.
> 
> This fixes the following static checker warning:
> net/ipv6/ip6_fib.c:1462 fib6_locate()
>          warn: variable dereferenced before check 'fn' (see line 1459)
> 
> net/ipv6/ip6_fib.c
>   1458          if (src_len) {
>   1459                  struct fib6_node *subtree = FIB6_SUBTREE(fn);
>                                                     ^^^^^^^^^^^^^^^^
> We shifted this dereference
> 
>   1460
>   1461                  WARN_ON(saddr == NULL);
>   1462                  if (fn && subtree)
>                             ^^
> before the check for NULL.
> 
>   1463                          fn = fib6_locate_1(subtree, saddr, src_len,
>   1464                                             offsetof(struct rt6_info, rt6i_src)
> 
> Fixes: 66f5d6ce53e6 ("ipv6: replace rwlock with rcu and spinlock in fib6_table")
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Wei Wang <weiwan@google.com>
> Acked-by: Eric Dumazet <edumazet@google.com>

Applied.