From d3843fe5fd45be0e04a251a2cc68893c859a31bd Mon Sep 17 00:00:00 2001 From: Wei Wang Date: Fri, 6 Oct 2017 12:06:06 -0700 Subject: ipv6: replace dst_hold() with dst_hold_safe() in routing code With rwlock, it is safe to call dst_hold() in the read thread because read thread is guaranteed to be separated from write thread. However, after we replace rwlock with rcu, it is no longer safe to use dst_hold(). A dst might already have been deleted but is waiting for the rcu grace period to pass before freeing the memory when a read thread is trying to do dst_hold(). This could potentially cause double free issue. So this commit replaces all dst_hold() with dst_hold_safe() in all read thread to avoid this double free issue. And in order to make the code more compact, a new function ip6_hold_safe() is introduced. It calls dst_hold_safe() first, and if that fails, it will either fall back to hold and return net->ipv6.ip6_null_entry or set rt to NULL according to the caller's need. Signed-off-by: Wei Wang Signed-off-by: Martin KaFai Lau Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv6/addrconf.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'net/ipv6/addrconf.c') diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 873afafddfc4..f86e931d555e 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -2333,7 +2333,8 @@ static struct rt6_info *addrconf_get_prefix_route(const struct in6_addr *pfx, continue; if ((rt->rt6i_flags & noflags) != 0) continue; - dst_hold(&rt->dst); + if (!dst_hold_safe(&rt->dst)) + rt = NULL; break; } out: -- cgit v1.2.3