Revision 4de8ebeff8ddefaceeb7fc6a9b1a514fc9624509 authored by Linus Torvalds on 22 February 2016, 22:09:18 UTC, committed by Linus Torvalds on 22 February 2016, 22:09:18 UTC
Pull tracing fixes from Steven Rostedt: "Two more small fixes. One is by Yang Shi who added a READ_ONCE_NOCHECK() to the scan of the stack made by the stack tracer. As the stack tracer scans the entire kernel stack, KASAN triggers seeing it as a "stack out of bounds" error. As the scan is looking at the contents of the stack from parent functions. The NOCHECK() tells KASAN that this is done on purpose, and is not some kind of stack overflow. The second fix is to the ftrace selftests, to retrieve the PID of executed commands from the shell with '$!' and not by parsing 'jobs'" * tag 'trace-fixes-v4.5-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing, kasan: Silence Kasan warning in check_stack of stack_tracer ftracetest: Fix instance test to use proper shell command for pids
xt_limit.c
/* (C) 1999 Jérôme de Vivie <devivie@info.enserb.u-bordeaux.fr>
* (C) 1999 Hervé Eychenne <eychenne@info.enserb.u-bordeaux.fr>
* (C) 2006-2012 Patrick McHardy <kaber@trash.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_limit.h>
struct xt_limit_priv {
unsigned long prev;
uint32_t credit;
};
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Herve Eychenne <rv@wallfire.org>");
MODULE_DESCRIPTION("Xtables: rate-limit match");
MODULE_ALIAS("ipt_limit");
MODULE_ALIAS("ip6t_limit");
/* The algorithm used is the Simple Token Bucket Filter (TBF)
* see net/sched/sch_tbf.c in the linux source tree
*/
static DEFINE_SPINLOCK(limit_lock);
/* Rusty: This is my (non-mathematically-inclined) understanding of
this algorithm. The `average rate' in jiffies becomes your initial
amount of credit `credit' and the most credit you can ever have
`credit_cap'. The `peak rate' becomes the cost of passing the
test, `cost'.
`prev' tracks the last packet hit: you gain one credit per jiffy.
If you get credit balance more than this, the extra credit is
discarded. Every time the match passes, you lose `cost' credits;
if you don't have that many, the test fails.
See Alexey's formal explanation in net/sched/sch_tbf.c.
To get the maxmum range, we multiply by this factor (ie. you get N
credits per jiffy). We want to allow a rate as low as 1 per day
(slowest userspace tool allows), which means
CREDITS_PER_JIFFY*HZ*60*60*24 < 2^32. ie. */
#define MAX_CPJ (0xFFFFFFFF / (HZ*60*60*24))
/* Repeated shift and or gives us all 1s, final shift and add 1 gives
* us the power of 2 below the theoretical max, so GCC simply does a
* shift. */
#define _POW2_BELOW2(x) ((x)|((x)>>1))
#define _POW2_BELOW4(x) (_POW2_BELOW2(x)|_POW2_BELOW2((x)>>2))
#define _POW2_BELOW8(x) (_POW2_BELOW4(x)|_POW2_BELOW4((x)>>4))
#define _POW2_BELOW16(x) (_POW2_BELOW8(x)|_POW2_BELOW8((x)>>8))
#define _POW2_BELOW32(x) (_POW2_BELOW16(x)|_POW2_BELOW16((x)>>16))
#define POW2_BELOW32(x) ((_POW2_BELOW32(x)>>1) + 1)
#define CREDITS_PER_JIFFY POW2_BELOW32(MAX_CPJ)
static bool
limit_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
const struct xt_rateinfo *r = par->matchinfo;
struct xt_limit_priv *priv = r->master;
unsigned long now = jiffies;
spin_lock_bh(&limit_lock);
priv->credit += (now - xchg(&priv->prev, now)) * CREDITS_PER_JIFFY;
if (priv->credit > r->credit_cap)
priv->credit = r->credit_cap;
if (priv->credit >= r->cost) {
/* We're not limited. */
priv->credit -= r->cost;
spin_unlock_bh(&limit_lock);
return true;
}
spin_unlock_bh(&limit_lock);
return false;
}
/* Precision saver. */
static u32 user2credits(u32 user)
{
/* If multiplying would overflow... */
if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY))
/* Divide first. */
return (user / XT_LIMIT_SCALE) * HZ * CREDITS_PER_JIFFY;
return (user * HZ * CREDITS_PER_JIFFY) / XT_LIMIT_SCALE;
}
static int limit_mt_check(const struct xt_mtchk_param *par)
{
struct xt_rateinfo *r = par->matchinfo;
struct xt_limit_priv *priv;
/* Check for overflow. */
if (r->burst == 0
|| user2credits(r->avg * r->burst) < user2credits(r->avg)) {
pr_info("Overflow, try lower: %u/%u\n",
r->avg, r->burst);
return -ERANGE;
}
priv = kmalloc(sizeof(*priv), GFP_KERNEL);
if (priv == NULL)
return -ENOMEM;
/* For SMP, we only want to use one set of state. */
r->master = priv;
/* User avg in seconds * XT_LIMIT_SCALE: convert to jiffies *
128. */
priv->prev = jiffies;
priv->credit = user2credits(r->avg * r->burst); /* Credits full. */
if (r->cost == 0) {
r->credit_cap = priv->credit; /* Credits full. */
r->cost = user2credits(r->avg);
}
return 0;
}
static void limit_mt_destroy(const struct xt_mtdtor_param *par)
{
const struct xt_rateinfo *info = par->matchinfo;
kfree(info->master);
}
#ifdef CONFIG_COMPAT
struct compat_xt_rateinfo {
u_int32_t avg;
u_int32_t burst;
compat_ulong_t prev;
u_int32_t credit;
u_int32_t credit_cap, cost;
u_int32_t master;
};
/* To keep the full "prev" timestamp, the upper 32 bits are stored in the
* master pointer, which does not need to be preserved. */
static void limit_mt_compat_from_user(void *dst, const void *src)
{
const struct compat_xt_rateinfo *cm = src;
struct xt_rateinfo m = {
.avg = cm->avg,
.burst = cm->burst,
.prev = cm->prev | (unsigned long)cm->master << 32,
.credit = cm->credit,
.credit_cap = cm->credit_cap,
.cost = cm->cost,
};
memcpy(dst, &m, sizeof(m));
}
static int limit_mt_compat_to_user(void __user *dst, const void *src)
{
const struct xt_rateinfo *m = src;
struct compat_xt_rateinfo cm = {
.avg = m->avg,
.burst = m->burst,
.prev = m->prev,
.credit = m->credit,
.credit_cap = m->credit_cap,
.cost = m->cost,
.master = m->prev >> 32,
};
return copy_to_user(dst, &cm, sizeof(cm)) ? -EFAULT : 0;
}
#endif /* CONFIG_COMPAT */
static struct xt_match limit_mt_reg __read_mostly = {
.name = "limit",
.revision = 0,
.family = NFPROTO_UNSPEC,
.match = limit_mt,
.checkentry = limit_mt_check,
.destroy = limit_mt_destroy,
.matchsize = sizeof(struct xt_rateinfo),
#ifdef CONFIG_COMPAT
.compatsize = sizeof(struct compat_xt_rateinfo),
.compat_from_user = limit_mt_compat_from_user,
.compat_to_user = limit_mt_compat_to_user,
#endif
.me = THIS_MODULE,
};
static int __init limit_mt_init(void)
{
return xt_register_match(&limit_mt_reg);
}
static void __exit limit_mt_exit(void)
{
xt_unregister_match(&limit_mt_reg);
}
module_init(limit_mt_init);
module_exit(limit_mt_exit);
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