Re: [PATCH] ipv6: do not free rt if FIB_LOOKUP_NOREF is set on suppress rule

[David Miller]

From: "Jason A. Donenfeld" <Jason@xxxxxxxxx>
Date: Tue, 24 Sep 2019 09:36:15 +0200

> 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@xxxxxxxxxxxxxxx
> 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@xxxxxxxxx>

Please make such test cases integratabe into the selftests area for networking
and submit it along with this fix.

Otherwise this code will regress.

Thank you.