Commit 14902008 authored by Francesco Ruggeri's avatar Francesco Ruggeri Committed by Luis Henriques

net: possible use after free in dst_release

commit 07a5d384 upstream.

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: d69bbf88 ("net: fix a race in dst_release()")
Fixes: 27b75c95 ("net: avoid RCU for NOCACHE dst")
Signed-off-by: default avatarFrancesco Ruggeri <fruggeri@arista.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent fd610413
...@@ -282,10 +282,11 @@ void dst_release(struct dst_entry *dst) ...@@ -282,10 +282,11 @@ void dst_release(struct dst_entry *dst)
{ {
if (dst) { if (dst) {
int newrefcnt; int newrefcnt;
unsigned short nocache = dst->flags & DST_NOCACHE;
newrefcnt = atomic_dec_return(&dst->__refcnt); newrefcnt = atomic_dec_return(&dst->__refcnt);
WARN_ON(newrefcnt < 0); WARN_ON(newrefcnt < 0);
if (!newrefcnt && unlikely(dst->flags & DST_NOCACHE)) if (!newrefcnt && unlikely(nocache))
call_rcu(&dst->rcu_head, dst_destroy_rcu); call_rcu(&dst->rcu_head, dst_destroy_rcu);
} }
} }
......
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