netdev - [PATCH net] ipv6: fix another slab-out-of-bounds in fib6_nh_flush

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Message-Id: <6f48619a725daf4bfaea7dad94504f722ab1b4f6.1626786511.git.pabeni@redhat.com>
Date:   Tue, 20 Jul 2021 15:08:40 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        David Ahern <dsahern@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Coco Li <lixiaoyan@...gle.com>
Subject: [PATCH net] ipv6: fix another slab-out-of-bounds in fib6_nh_flush_exceptions

While running the self-tests on a KASAN enabled kernel, I observed a
slab-out-of-bounds splat very similar to the one reported in
commit 821bbf79fe46 ("ipv6: Fix KASAN: slab-out-of-bounds Read in
 fib6_nh_flush_exceptions").

We additionally need to take care of fib6_metrics initialization
failure when the caller provides an nh.

The fix is similar, explicitly free the route instead of calling
fib6_info_release on a half-initialized object.

Fixes: f88d8ea67fbdb ("ipv6: Plumb support for nexthop object in a fib6_info")
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 net/ipv6/route.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 7b756a7dc036..b6ddf23d3833 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3769,7 +3769,7 @@ static struct fib6_info *ip6_route_info_create(struct fib6_config *cfg,
 		err = PTR_ERR(rt->fib6_metrics);
 		/* Do not leave garbage there. */
 		rt->fib6_metrics = (struct dst_metrics *)&dst_default_metrics;
-		goto out;
+		goto out_free;
 	}
 
 	if (cfg->fc_flags & RTF_ADDRCONF)
-- 
2.26.3