net: possible use after free in dst_release

[ Upstream commit 07a5d38453599052aff0877b16bb9c1585f08609 ]

dst_release should not access dst->flags after decrementing
__refcnt to 0. The dst_entry may be in dst_busy_list and
dst_gc_task may dst_destroy it before dst_release gets a chance
to access dst->flags.

Fixes: d69bbf88c8d0 ("net: fix a race in dst_release()")
Fixes: 27b75c95f1 ("net: avoid RCU for NOCACHE dst")
Signed-off-by: Francesco Ruggeri <fruggeri@arista.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Francesco Ruggeri 2016-01-06 00:18:48 -08:00 committed by Greg Kroah-Hartman
parent a15061500d
commit 439af14e3b
1 changed files with 2 additions and 1 deletions

View File

@ -280,10 +280,11 @@ void dst_release(struct dst_entry *dst)
{
if (dst) {
int newrefcnt;
unsigned short nocache = dst->flags & DST_NOCACHE;
newrefcnt = atomic_dec_return(&dst->__refcnt);
WARN_ON(newrefcnt < 0);
if (!newrefcnt && unlikely(dst->flags & DST_NOCACHE))
if (!newrefcnt && unlikely(nocache))
call_rcu(&dst->rcu_head, dst_destroy_rcu);
}
}