Commit c3c14da0 authored Apr 23, 2018 by David Ahern Committed by David S. Miller Apr 23, 2018

net/ipv6: add rcu locking to ip6_negative_advice



syzbot reported a suspicious rcu_dereference_check:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x1b9/0x294 lib/dump_stack.c:113
  lockdep_rcu_suspicious+0x14a/0x153 kernel/locking/lockdep.c:4592
  rt6_check_expired+0x38b/0x3e0 net/ipv6/route.c:410
  ip6_negative_advice+0x67/0xc0 net/ipv6/route.c:2204
  dst_negative_advice include/net/sock.h:1786 [inline]
  sock_setsockopt+0x138f/0x1fe0 net/core/sock.c:1051
  __sys_setsockopt+0x2df/0x390 net/socket.c:1899
  SYSC_setsockopt net/socket.c:1914 [inline]
  SyS_setsockopt+0x34/0x50 net/socket.c:1911

Add rcu locking around call to rt6_check_expired in
ip6_negative_advice.

Fixes: a68886a6 ("net/ipv6: Make from in rt6_info rcu protected")
Reported-by:  <syzbot+2422c9e35796659d2273@syzkaller.appspotmail.com>
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 40cde824

net/ipv6/route.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -2201,10 +2201,12 @@ static struct dst_entry ip6_negative_advice(struct dst_entry dst)

		if (rt) {
		if (rt->rt6i_flags & RTF_CACHE) {
		rcu_read_lock();
		if (rt6_check_expired(rt)) {
		rt6_remove_exception_rt(rt);
		dst = NULL;
		}
		rcu_read_unlock();
		} else {
		dst_release(dst);
		dst = NULL;

Admin message