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net: fix decnet rtnexthop parsing

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dn_fib_count_nhs() could enter an infinite loop if nhp->rtnh_len == 0
(i.e. if userspace passes a malformed netlink message).

Let's use the helpers from net/nexthop.h which take care of all this
stuff. We can do exactly the same as e.g. fib_count_nexthops() and
fib_get_nhs() from net/ipv4/fib_semantics.c.

This fixes the softlockup for me.

Cc: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vegard Nossum 2016-07-05 21:12:53 +02:00 committed by David S. Miller
parent f5d6516120
commit ab58298cf4
1 changed files with 12 additions and 9 deletions
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21
net/decnet/dn_fib.c
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@ -41,6 +41,7 @@
#include <net/dn_fib.h>
#include <net/dn_neigh.h>
#include <net/dn_dev.h>
#include <net/nexthop.h>
#define RT_MIN_TABLE 1
@ -150,14 +151,13 @@ static int dn_fib_count_nhs(const struct nlattr *attr)
struct rtnexthop *nhp = nla_data(attr);
int nhs = 0, nhlen = nla_len(attr);
while(nhlen >= (int)sizeof(struct rtnexthop)) {
if ((nhlen -= nhp->rtnh_len) < 0)
return 0;
while (rtnh_ok(nhp, nhlen)) {
nhs++;
nhp = RTNH_NEXT(nhp);
nhp = rtnh_next(nhp, &nhlen);
}
return nhs;
/* leftover implies invalid nexthop configuration, discard it */
return nhlen > 0 ? 0 : nhs;
}
static int dn_fib_get_nhs(struct dn_fib_info *fi, const struct nlattr *attr,
@ -167,21 +167,24 @@ static int dn_fib_get_nhs(struct dn_fib_info *fi, const struct nlattr *attr,
int nhlen = nla_len(attr);
change_nexthops(fi) {
int attrlen = nhlen - sizeof(struct rtnexthop);
if (attrlen < 0 || (nhlen -= nhp->rtnh_len) < 0)
int attrlen;
if (!rtnh_ok(nhp, nhlen))
return -EINVAL;
nh->nh_flags = (r->rtm_flags&~0xFF) | nhp->rtnh_flags;
nh->nh_oif = nhp->rtnh_ifindex;
nh->nh_weight = nhp->rtnh_hops + 1;
if (attrlen) {
attrlen = rtnh_attrlen(nhp);
if (attrlen > 0) {
struct nlattr *gw_attr;
gw_attr = nla_find((struct nlattr *) (nhp + 1), attrlen, RTA_GATEWAY);
nh->nh_gw = gw_attr ? nla_get_le16(gw_attr) : 0;
}
nhp = RTNH_NEXT(nhp);
nhp = rtnh_next(nhp, &nhlen);
} endfor_nexthops(fi);
return 0;