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Date: Wed, 06 Jan 2016 05:57:24 -0800 From: Eric Dumazet <eric.dumazet@...il.com> To: Francesco Ruggeri <fruggeri@...stanetworks.com> Cc: fruggeri@...sta.com, edumazet@...gle.com, davem@...emloft.net, netdev@...r.kernel.org Subject: Re: [PATCH 1/1] net: possible use after free in dst_release On Wed, 2016-01-06 at 00:18 -0800, Francesco Ruggeri wrote: > 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. > > Signed-off-by: Francesco Ruggeri <fruggeri@...sta.com> > --- > net/core/dst.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/net/core/dst.c b/net/core/dst.c > index e6dc772..a1656e3 100644 > --- a/net/core/dst.c > +++ b/net/core/dst.c > @@ -301,12 +301,13 @@ void dst_release(struct dst_entry *dst) > { > if (dst) { > int newrefcnt; > + unsigned short nocache = dst->flags & DST_NOCACHE; > > newrefcnt = atomic_dec_return(&dst->__refcnt); > if (unlikely(newrefcnt < 0)) > net_warn_ratelimited("%s: dst:%p refcnt:%d\n", > __func__, dst, newrefcnt); > - if (!newrefcnt && unlikely(dst->flags & DST_NOCACHE)) > + if (!newrefcnt && unlikely(nocache)) > call_rcu(&dst->rcu_head, dst_destroy_rcu); > } > } You're right. My previous fix (commit d69bbf88c8d0) was okay only for DST_NOCACHE dst. Fixes: d69bbf88c8d0 ("net: fix a race in dst_release()") Fixes: 27b75c95f10d ("net: avoid RCU for NOCACHE dst") Acked-by: Eric Dumazet <edumazet@...gle.com> Thanks ! -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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