On Tue, Nov 23, 2021 at 12:27:19PM +0200, Nikolay Aleksandrov wrote:
From: Nikolay Aleksandrov nikolay@nvidia.com
When we try to add an IPv6 nexthop and IPv6 is not enabled (!CONFIG_IPV6) we'll hit a NULL pointer dereference[1] in the error path of nh_create_ipv6() due to calling ipv6_stub->fib6_nh_release. The bug has been present since the beginning of IPv6 nexthop gateway support. Commit 1aefd3de7bc6 ("ipv6: Add fib6_nh_init and release to stubs") tells us that only fib6_nh_init has a dummy stub because fib6_nh_release should not be called if fib6_nh_init returns an error, but the commit below added a call to ipv6_stub->fib6_nh_release in its error path. To fix it return the dummy stub's -EAFNOSUPPORT error directly without calling ipv6_stub->fib6_nh_release in nh_create_ipv6()'s error path.
[...]
diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c index a69a9e76f99f..5dbd4b5505eb 100644 --- a/net/ipv4/nexthop.c +++ b/net/ipv4/nexthop.c @@ -2565,11 +2565,15 @@ static int nh_create_ipv6(struct net *net, struct nexthop *nh, /* sets nh_dev if successful */ err = ipv6_stub->fib6_nh_init(net, fib6_nh, &fib6_cfg, GFP_KERNEL, extack);
- if (err)
- if (err) {
/* IPv6 is not enabled, don't call fib6_nh_release */if (err == -EAFNOSUPPORT)goto out;
Is the call actually necessary? If fib6_nh_init() failed, then I believe it should clean up after itself and not rely on fib6_nh_release().
- else
- } else { nh->nh_flags = fib6_nh->fib_nh_flags;
- }
+out: return err; } -- 2.31.1