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Commit 82486aa6 authored by WANG Cong's avatar WANG Cong Committed by David S. Miller
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ipv4: restore rt->fi for reference counting



IPv4 dst could use fi->fib_metrics to store metrics but fib_info
itself is refcnt'ed, so without taking a refcnt fi and
fi->fib_metrics could be freed while dst metrics still points to
it. This triggers use-after-free as reported by Andrey twice.

This patch reverts commit 2860583f ("ipv4: Kill rt->fi") to
restore this reference counting. It is a quick fix for -net and
-stable, for -net-next, as Eric suggested, we can consider doing
reference counting for metrics itself instead of relying on fib_info.

IPv6 is very different, it copies or steals the metrics from mx6_config
in fib6_commit_metrics() so probably doesn't need a refcnt.

Decnet has already done the refcnt'ing, see dn_fib_semantic_match().

Fixes: 2860583f ("ipv4: Kill rt->fi")
Reported-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Tested-by: default avatarAndrey Konovalov <andreyknvl@google.com>
Signed-off-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3013c498
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