From: Eric Dumazet <eric.duma...@gmail.com>
Date: Wed, 06 Jan 2016 05:57:24 -0800
> 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 <frugg...@arista.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 <eduma...@google.com>
Applied and queued up for -stable, thanks everyone!
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