From 0409c9a5a7546043d32e8c46df0dcaf65f97f659 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Mon, 5 Jan 2015 23:57:43 +0100 Subject: [PATCH] net: fib6: fib6_commit_metrics: fix potential NULL pointer dereference MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit When IPv6 host routes with metrics attached are being added, we fetch the metrics store from the dst via COW through dst_metrics_write_ptr(), added through commit e5fd387ad5b3. One remaining problem here is that we actually call into inet_getpeer() and may end up allocating/creating a new peer from the kmemcache, which may fail. Example trace from perf probe (inet_getpeer:41) where create is 1: ip 6877 [002] 4221.391591: probe:inet_getpeer: (ffffffff8165e293) 85e294 inet_getpeer.part.7 (<- kmem_cache_alloc()) 85e578 inet_getpeer 8eb333 ipv6_cow_metrics 8f10ff fib6_commit_metrics Therefore, a check for NULL on the return of dst_metrics_write_ptr() is necessary here. Joint work with Florian Westphal. Fixes: e5fd387ad5b3 ("ipv6: do not overwrite inetpeer metrics prematurely") Cc: Michal Kubeček Signed-off-by: Florian Westphal Signed-off-by: Daniel Borkmann Signed-off-by: David S. Miller --- net/ipv6/ip6_fib.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c index b2d1838897c9..db4984e13f2f 100644 --- a/net/ipv6/ip6_fib.c +++ b/net/ipv6/ip6_fib.c @@ -633,18 +633,17 @@ static bool rt6_qualify_for_ecmp(struct rt6_info *rt) static int fib6_commit_metrics(struct dst_entry *dst, struct nlattr *mx, int mx_len) { + bool dst_host = dst->flags & DST_HOST; struct nlattr *nla; int remaining; u32 *mp; - if (dst->flags & DST_HOST) { - mp = dst_metrics_write_ptr(dst); - } else { - mp = kzalloc(sizeof(u32) * RTAX_MAX, GFP_ATOMIC); - if (!mp) - return -ENOMEM; + mp = dst_host ? dst_metrics_write_ptr(dst) : + kzalloc(sizeof(u32) * RTAX_MAX, GFP_ATOMIC); + if (unlikely(!mp)) + return -ENOMEM; + if (!dst_host) dst_init_metrics(dst, mp, 0); - } nla_for_each_attr(nla, mx, mx_len, remaining) { int type = nla_type(nla); -- 2.20.1