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net: fib6: fib6_commit_metrics: fix potential NULL pointer dereference

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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 e5fd387ad5.

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: e5fd387ad5 ("ipv6: do not overwrite inetpeer metrics prematurely")
Cc: Michal Kubeček <mkubecek@suse.cz>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann 2015-01-05 23:57:43 +01:00 committed by David S. Miller
parent 6cb69742da
commit 0409c9a5a7
1 changed files with 6 additions and 7 deletions
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13
net/ipv6/ip6_fib.c
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@ -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);