net: possible use after free in dst_release
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:d69bbf88c8
("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>
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07a5d38453
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@ -301,12 +301,13 @@ void dst_release(struct dst_entry *dst)
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{
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{
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if (dst) {
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if (dst) {
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int newrefcnt;
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int newrefcnt;
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unsigned short nocache = dst->flags & DST_NOCACHE;
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newrefcnt = atomic_dec_return(&dst->__refcnt);
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newrefcnt = atomic_dec_return(&dst->__refcnt);
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if (unlikely(newrefcnt < 0))
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if (unlikely(newrefcnt < 0))
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net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
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net_warn_ratelimited("%s: dst:%p refcnt:%d\n",
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__func__, dst, newrefcnt);
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__func__, dst, newrefcnt);
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if (!newrefcnt && unlikely(dst->flags & DST_NOCACHE))
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if (!newrefcnt && unlikely(nocache))
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call_rcu(&dst->rcu_head, dst_destroy_rcu);
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call_rcu(&dst->rcu_head, dst_destroy_rcu);
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}
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}
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}
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}
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