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SubjectRe: [PATCH] ipv6: do not free rt if FIB_LOOKUP_NOREF is set on suppress rule
Hey Wei,

I meant to CC you but slipped up. Sorry about that. Take a look at
this thread if you have a chance.

Thanks,
Jason

On Tue, Sep 24, 2019 at 10:03 AM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>
> Commit 7d9e5f422150 removed references from certain dsts, but accounting
> for this never translated down into the fib6 suppression code. This bug
> was triggered by WireGuard users who use wg-quick(8), which uses the
> "suppress-prefix" directive to ip-rule(8) for routing all of their
> internet traffic without routing loops. The test case in the link of
> this commit reliably triggers various crashes due to the use-after-free
> caused by the reference underflow.
>
> Cc: stable@vger.kernel.org
> Fixes: 7d9e5f422150 ("ipv6: convert major tx path to use RT6_LOOKUP_F_DST_NOREF")
> Test-case: https://git.zx2c4.com/WireGuard/commit/?id=ad66532000f7a20b149e47c5eb3a957362c8e161
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
> net/ipv6/fib6_rules.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv6/fib6_rules.c b/net/ipv6/fib6_rules.c
> index d22b6c140f23..f9e8fe3ff0c5 100644
> --- a/net/ipv6/fib6_rules.c
> +++ b/net/ipv6/fib6_rules.c
> @@ -287,7 +287,8 @@ static bool fib6_rule_suppress(struct fib_rule *rule, struct fib_lookup_arg *arg
> return false;
>
> suppress_route:
> - ip6_rt_put(rt);
> + if (!(arg->flags & FIB_LOOKUP_NOREF))
> + ip6_rt_put(rt);
> return true;
> }
>
> --
> 2.21.0

On Tue, Sep 24, 2019 at 10:03 AM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>
> Commit 7d9e5f422150 removed references from certain dsts, but accounting
> for this never translated down into the fib6 suppression code. This bug
> was triggered by WireGuard users who use wg-quick(8), which uses the
> "suppress-prefix" directive to ip-rule(8) for routing all of their
> internet traffic without routing loops. The test case in the link of
> this commit reliably triggers various crashes due to the use-after-free
> caused by the reference underflow.
>
> Cc: stable@vger.kernel.org
> Fixes: 7d9e5f422150 ("ipv6: convert major tx path to use RT6_LOOKUP_F_DST_NOREF")
> Test-case: https://git.zx2c4.com/WireGuard/commit/?id=ad66532000f7a20b149e47c5eb3a957362c8e161
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
> ---
> net/ipv6/fib6_rules.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv6/fib6_rules.c b/net/ipv6/fib6_rules.c
> index d22b6c140f23..f9e8fe3ff0c5 100644
> --- a/net/ipv6/fib6_rules.c
> +++ b/net/ipv6/fib6_rules.c
> @@ -287,7 +287,8 @@ static bool fib6_rule_suppress(struct fib_rule *rule, struct fib_lookup_arg *arg
> return false;
>
> suppress_route:
> - ip6_rt_put(rt);
> + if (!(arg->flags & FIB_LOOKUP_NOREF))
> + ip6_rt_put(rt);
> return true;
> }
>
> --
> 2.21.0



--
Jason A. Donenfeld
Deep Space Explorer
fr: +33 6 51 90 82 66
us: +1 513 476 1200

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