Commit 54851aa9 authored Jul 17, 2019 by Ido Schimmel Committed by David S. Miller Jul 18, 2019

ipv6: Unlink sibling route in case of failure



When a route needs to be appended to an existing multipath route,
fib6_add_rt2node() first appends it to the siblings list and increments
the number of sibling routes on each sibling.

Later, the function notifies the route via call_fib6_entry_notifiers().
In case the notification is vetoed, the route is not unlinked from the
siblings list, which can result in a use-after-free.

Fix this by unlinking the route from the siblings list before returning
an error.

Audited the rest of the call sites from which the FIB notification chain
is called and could not find more problems.

Fixes: 2233000c ("net/ipv6: Move call_fib6_entry_notifiers up for route adds")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reported-by: Alexander Petrovskiy <alexpe@mellanox.com>
Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 9c2a57d1

net/ipv6/ip6_fib.c

+17 −1

Original line number	Diff line number	Diff line
		@@ -1151,8 +1151,24 @@ add:
		err = call_fib6_entry_notifiers(info->nl_net,
		FIB_EVENT_ENTRY_ADD,
		rt, extack);
		if (err)
		if (err) {
		struct fib6_info sibling, next_sibling;

		/* If the route has siblings, then it first
		* needs to be unlinked from them.
		*/
		if (!rt->fib6_nsiblings)
		return err;

		list_for_each_entry_safe(sibling, next_sibling,
		&rt->fib6_siblings,
		fib6_siblings)
		sibling->fib6_nsiblings--;
		rt->fib6_nsiblings = 0;
		list_del_init(&rt->fib6_siblings);
		rt6_multipath_rebalance(next_sibling);
		return err;
		}
		}

		rcu_assign_pointer(rt->fib6_next, iter);

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