[PATCH net-next] net/ipv6: insert the fib6 gc_link of a fib6_info only if in fib6.

[thinker.li@gmail.com]

From: Kui-Feng Lee <thinker.li@gmail.com>

Check f6i->fib6_node before inserting a f6i (fib6_info) to tb6_gc_hlist.

Previously, it checks only if f6i->fib6_table is not NULL, however it is
not enough. When a f6i is removed from a fib6_table, it's fib6_table is not
going to be reset. fib6_node is always reset when a f6i is removed from a
fib6_table and set when a f6i is added to a fib6_table. By checking
fib6_node, adding a f6i t0 tb6_gc_hlist only if f6i is in the table will be
enforced.

Fixes: 3dec89b14d37 ("net/ipv6: Remove expired routes with a separated list of routes.")
Reported-by: syzbot+c15aa445274af8674f41@syzkaller.appspotmail.com
Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: dsahern@kernel.org
---
 include/net/ip6_fib.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 95ed495c3a40..8477c9ff67ac 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -512,7 +512,10 @@ static inline void fib6_set_expires_locked(struct fib6_info *f6i,
 
 	tb6 = f6i->fib6_table;
 	f6i->expires = expires;
-	if (tb6 && !fib6_has_expires(f6i))
+	if (tb6 &&
+	    rcu_dereference_protected(f6i->fib6_node,
+				      lockdep_is_held(&tb6->tb6_lock)) &&
+	    !fib6_has_expires(f6i))
 		hlist_add_head(&f6i->gc_link, &tb6->tb6_gc_hlist);
 	f6i->fib6_flags |= RTF_EXPIRES;
 }
-- 
2.34.1