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=ad66532000f7a20b149e47c5eb3a95736... 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; }