From 1c87e79a002f6a159396138cd3f3ab554a2a8887 Mon Sep 17 00:00:00 2001 From: Xin Long Date: Wed, 20 Mar 2019 14:45:48 +0800 Subject: [PATCH] ipv6: make ip6_create_rt_rcu return ip6_null_entry instead of NULL Jianlin reported a crash: [ 381.484332] BUG: unable to handle kernel NULL pointer dereference at 0000000000000068 [ 381.619802] RIP: 0010:fib6_rule_lookup+0xa3/0x160 [ 382.009615] Call Trace: [ 382.020762] [ 382.030174] ip6_route_redirect.isra.52+0xc9/0xf0 [ 382.050984] ip6_redirect+0xb6/0xf0 [ 382.066731] icmpv6_notify+0xca/0x190 [ 382.083185] ndisc_redirect_rcv+0x10f/0x160 [ 382.102569] ndisc_rcv+0xfb/0x100 [ 382.117725] icmpv6_rcv+0x3f2/0x520 [ 382.133637] ip6_input_finish+0xbf/0x460 [ 382.151634] ip6_input+0x3b/0xb0 [ 382.166097] ipv6_rcv+0x378/0x4e0 It was caused by the lookup function __ip6_route_redirect() returns NULL in fib6_rule_lookup() when ip6_create_rt_rcu() returns NULL. So we fix it by simply making ip6_create_rt_rcu() return ip6_null_entry instead of NULL. v1->v2: - move down 'fallback:' to make it more readable. Fixes: e873e4b9cc7e ("ipv6: use fib6_info_hold_safe() when necessary") Reported-by: Jianlin Shi Suggested-by: Paolo Abeni Signed-off-by: Xin Long Reviewed-by: David Ahern Acked-by: Wei Wang Signed-off-by: David S. Miller --- net/ipv6/route.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 4ef4bbdb49d4..0302e0eb07af 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -1040,14 +1040,20 @@ static struct rt6_info *ip6_create_rt_rcu(struct fib6_info *rt) struct rt6_info *nrt; if (!fib6_info_hold_safe(rt)) - return NULL; + goto fallback; nrt = ip6_dst_alloc(dev_net(dev), dev, flags); - if (nrt) - ip6_rt_copy_init(nrt, rt); - else + if (!nrt) { fib6_info_release(rt); + goto fallback; + } + ip6_rt_copy_init(nrt, rt); + return nrt; + +fallback: + nrt = dev_net(dev)->ipv6.ip6_null_entry; + dst_hold(&nrt->dst); return nrt; } @@ -1096,10 +1102,6 @@ restart: dst_hold(&rt->dst); } else { rt = ip6_create_rt_rcu(f6i); - if (!rt) { - rt = net->ipv6.ip6_null_entry; - dst_hold(&rt->dst); - } } rcu_read_unlock(); -- 2.30.2