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SubjectRe: [PATCH] ipv6: Properly check reference count flag before taking reference
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On 9/23/19 8:06 AM, Petr Vorel wrote:
> Hi,
>
>> People are reporting that WireGuard experiences erratic crashes on 5.3,
>> and bisected it down to 7d30a7f6424e. Casually flipping through that
>> commit I noticed that a flag is checked using `|` instead of `&`, which in
>> this current case, means that a reference is never incremented, which
>> would result in the use-after-free users are seeing. This commit changes
>> the `|` to the proper `&` test.
>
>> Cc: stable@vger.kernel.org
>> Fixes: 7d30a7f6424e ("Merge branch 'ipv6-avoid-taking-refcnt-on-dst-during-route-lookup'")
>> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
>
> Reviewed-by: Petr Vorel <pvorel@suse.cz>
>
> NOTE: this change was added in d64a1f574a29 ("ipv6: honor RT6_LOOKUP_F_DST_NOREF in rule lookup logic")
>
> Kind regards,
> Petr
>

This was fixed earlier I think

https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/commit/?id=7b09c2d052db4b4ad0b27b97918b46a7746966fa

>> ---
>> net/ipv6/ip6_fib.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>> diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
>> index 87f47bc55c5e..6e2af411cd9c 100644
>> --- a/net/ipv6/ip6_fib.c
>> +++ b/net/ipv6/ip6_fib.c
>> @@ -318,7 +318,7 @@ struct dst_entry *fib6_rule_lookup(struct net *net, struct flowi6 *fl6,
>> if (rt->dst.error == -EAGAIN) {
>> ip6_rt_put_flags(rt, flags);
>> rt = net->ipv6.ip6_null_entry;
>> - if (!(flags | RT6_LOOKUP_F_DST_NOREF))
>> + if (!(flags & RT6_LOOKUP_F_DST_NOREF))
>> dst_hold(&rt->dst);
>> }

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