ipv4: fix NULL dereference in free_fib_info_rcu()
authorEric Dumazet <edumazet@google.com>
Tue, 15 Aug 2017 12:26:17 +0000 (05:26 -0700)
committerDavid S. Miller <davem@davemloft.net>
Wed, 16 Aug 2017 00:07:52 +0000 (17:07 -0700)
commit187e5b3ac84d3421d2de3aca949b2791fbcad554
tree44a56af785355119f067c75a799d55fd3789ca86
parentb3dc8f772fab5b2d284b780830fd56494491e493
ipv4: fix NULL dereference in free_fib_info_rcu()

If fi->fib_metrics could not be allocated in fib_create_info()
we attempt to dereference a NULL pointer in free_fib_info_rcu() :

    m = fi->fib_metrics;
    if (m != &dst_default_metrics && atomic_dec_and_test(&m->refcnt))
            kfree(m);

Before my recent patch, we used to call kfree(NULL) and nothing wrong
happened.

Instead of using RCU to defer freeing while we are under memory stress,
it seems better to take immediate action.

This was reported by syzkaller team.

Fixes: 3fb07daff8e9 ("ipv4: add reference counting to metrics")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/ipv4/fib_semantics.c