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authorWillem de Bruijn <willemb@google.com>2013-06-13 15:29:38 -0400
committerDavid S. Miller <davem@davemloft.net>2013-06-13 17:13:05 -0700
commit5f121b9a83b499a61ed44e5ba619c7de8f7271ad (patch)
tree6765d95f468e5c8c884af26f5fbfd2c6428d255d /net/core
parent85f16525a2eb66e6092cbd8dcf42371df8334ed0 (diff)
net-rps: fixes for rps flow limit
Caught by sparse: - __rcu: missing annotation to sd->flow_limit - __user: direct access in cpumask_scnprintf Also - add endline character when printing bitmap if room in buffer - avoid bucket overflow by reducing FLOW_LIMIT_HISTORY The last item warrants some explanation. The hashtable buckets are subject to overflow if FLOW_LIMIT_HISTORY is larger than or equal to bucket size, since all packets may end up in a single bucket. The current (rather arbitrary) history value of 256 happens to match the buffer size (u8). As a result, with a single flow, the first 128 packets are accepted (correct), the second 128 packets dropped (correct) and then the history[] array has filled, so that each subsequent new packet causes an increment in the bucket for new_flow plus a decrement for old_flow: a steady state. This is fine if packets are dropped, as the steady state goes away as soon as a mix of traffic reappears. But, because the 256th packet overflowed the bucket to 0: no packets are dropped. Instead of explicitly adding an overflow check, this patch changes FLOW_LIMIT_HISTORY to never be able to overflow a single bucket. Reported-by: Fengguang Wu <fengguang.wu@intel.com> (first item) Signed-off-by: Willem de Bruijn <willemb@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/sysctl_net_core.c19
1 files changed, 16 insertions, 3 deletions
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 637a42e5d58..78c746e016a 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -132,6 +132,8 @@ static int flow_limit_cpu_sysctl(struct ctl_table *table, int write,
write_unlock:
mutex_unlock(&flow_limit_update_mutex);
} else {
+ char kbuf[128];
+
if (*ppos || !*lenp) {
*lenp = 0;
goto done;
@@ -146,9 +148,20 @@ write_unlock:
}
rcu_read_unlock();
- len = cpumask_scnprintf(buffer, *lenp, mask);
- *lenp = len + 1;
- *ppos += len + 1;
+ len = min(sizeof(kbuf) - 1, *lenp);
+ len = cpumask_scnprintf(kbuf, len, mask);
+ if (!len) {
+ *lenp = 0;
+ goto done;
+ }
+ if (len < *lenp)
+ kbuf[len++] = '\n';
+ if (copy_to_user(buffer, kbuf, len)) {
+ ret = -EFAULT;
+ goto done;
+ }
+ *lenp = len;
+ *ppos += len;
}
done: