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net: neighbour: prohibit negative value for unres_qlen_bytes parameter

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unres_qlen_bytes and unres_qlen are int type.
But multiple relation(unres_qlen_bytes = unres_qlen * SKB_TRUESIZE(ETH_FRAME_LEN))
will cause type overflow when seting unres_qlen. e.g.

$ echo 1027506 > /proc/sys/net/ipv4/neigh/eth1/unres_qlen
$ cat /proc/sys/net/ipv4/neigh/eth1/unres_qlen
1182657265
$ cat /proc/sys/net/ipv4/neigh/eth1/unres_qlen_bytes
-2147479756

The gutted value is not that we setting。
But user/administrator don't know this is caused by int type overflow.

what's more, it is meaningless and even dangerous that unres_qlen_bytes is set
with negative number. Because, for unresolved neighbour address, kernel will cache packets
without limit in __neigh_event_send()(e.g. (u32)-1 = 2GB).

Signed-off-by: Shan Wei <davidshan@tencent.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Shan Wei 2012-12-04 18:49:15 +00:00 committed by David S. Miller
parent 1642182ea0
commit ce46cc64d4
1 changed files with 12 additions and 5 deletions
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17
net/core/neighbour.c
View file

@ -62,6 +62,9 @@ static void __neigh_notify(struct neighbour *n, int type, int flags);
static void neigh_update_notify(struct neighbour *neigh);
static int pneigh_ifdown(struct neigh_table *tbl, struct net_device *dev);
static int zero;
static int unres_qlen_max = INT_MAX / SKB_TRUESIZE(ETH_FRAME_LEN);
static struct neigh_table *neigh_tables;
#ifdef CONFIG_PROC_FS
static const struct file_operations neigh_stat_seq_fops;
@ -1787,8 +1790,7 @@ static int neightbl_fill_parms(struct sk_buff *skb, struct neigh_parms *parms)
nla_put_u32(skb, NDTPA_QUEUE_LENBYTES, parms->queue_len_bytes) ||
/* approximative value for deprecated QUEUE_LEN (in packets) */
nla_put_u32(skb, NDTPA_QUEUE_LEN,
DIV_ROUND_UP(parms->queue_len_bytes,
SKB_TRUESIZE(ETH_FRAME_LEN))) ||
parms->queue_len_bytes / SKB_TRUESIZE(ETH_FRAME_LEN)) ||
nla_put_u32(skb, NDTPA_PROXY_QLEN, parms->proxy_qlen) ||
nla_put_u32(skb, NDTPA_APP_PROBES, parms->app_probes) ||
nla_put_u32(skb, NDTPA_UCAST_PROBES, parms->ucast_probes) ||
@ -2777,9 +2779,13 @@ static int proc_unres_qlen(ctl_table *ctl, int write, void __user *buffer,
int size, ret;
ctl_table tmp = *ctl;
tmp.extra1 = &zero;
tmp.extra2 = &unres_qlen_max;
tmp.data = &size;
size = DIV_ROUND_UP(*(int *)ctl->data, SKB_TRUESIZE(ETH_FRAME_LEN));
ret = proc_dointvec(&tmp, write, buffer, lenp, ppos);
size = *(int *)ctl->data / SKB_TRUESIZE(ETH_FRAME_LEN);
ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
if (write && !ret)
*(int *)ctl->data = size * SKB_TRUESIZE(ETH_FRAME_LEN);
return ret;
@ -2865,7 +2871,8 @@ static struct neigh_sysctl_table {
.procname = "unres_qlen_bytes",
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
.extra1 = &zero,
.proc_handler = proc_dointvec_minmax,
},
[NEIGH_VAR_PROXY_QLEN] = {
.procname = "proxy_qlen",