diff options
author | Willem de Bruijn <willemb@google.com> | 2013-06-13 21:29:38 +0200 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2013-06-14 02:13:05 +0200 |
commit | 5f121b9a83b499a61ed44e5ba619c7de8f7271ad (patch) | |
tree | 6765d95f468e5c8c884af26f5fbfd2c6428d255d /net/core | |
parent | tcp: properly send new data in fast recovery in first RTT (diff) | |
download | linux-5f121b9a83b499a61ed44e5ba619c7de8f7271ad.tar.xz linux-5f121b9a83b499a61ed44e5ba619c7de8f7271ad.zip |
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.c | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c index 637a42e5d589..78c746e016ae 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: |