linux/net/core/sysctl_net_core.c
Daniel Borkmann 74451e66d5 bpf: make jited programs visible in traces
Long standing issue with JITed programs is that stack traces from
function tracing check whether a given address is kernel code
through {__,}kernel_text_address(), which checks for code in core
kernel, modules and dynamically allocated ftrace trampolines. But
what is still missing is BPF JITed programs (interpreted programs
are not an issue as __bpf_prog_run() will be attributed to them),
thus when a stack trace is triggered, the code walking the stack
won't see any of the JITed ones. The same for address correlation
done from user space via reading /proc/kallsyms. This is read by
tools like perf, but the latter is also useful for permanent live
tracing with eBPF itself in combination with stack maps when other
eBPF types are part of the callchain. See offwaketime example on
dumping stack from a map.

This work tries to tackle that issue by making the addresses and
symbols known to the kernel. The lookup from *kernel_text_address()
is implemented through a latched RB tree that can be read under
RCU in fast-path that is also shared for symbol/size/offset lookup
for a specific given address in kallsyms. The slow-path iteration
through all symbols in the seq file done via RCU list, which holds
a tiny fraction of all exported ksyms, usually below 0.1 percent.
Function symbols are exported as bpf_prog_<tag>, in order to aide
debugging and attribution. This facility is currently enabled for
root-only when bpf_jit_kallsyms is set to 1, and disabled if hardening
is active in any mode. The rationale behind this is that still a lot
of systems ship with world read permissions on kallsyms thus addresses
should not get suddenly exposed for them. If that situation gets
much better in future, we always have the option to change the
default on this. Likewise, unprivileged programs are not allowed
to add entries there either, but that is less of a concern as most
such programs types relevant in this context are for root-only anyway.
If enabled, call graphs and stack traces will then show a correct
attribution; one example is illustrated below, where the trace is
now visible in tooling such as perf script --kallsyms=/proc/kallsyms
and friends.

Before:

  7fff8166889d bpf_clone_redirect+0x80007f0020ed (/lib/modules/4.9.0-rc8+/build/vmlinux)
         f5d80 __sendmsg_nocancel+0xffff006451f1a007 (/usr/lib64/libc-2.18.so)

After:

  7fff816688b7 bpf_clone_redirect+0x80007f002107 (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fffa0575728 bpf_prog_33c45a467c9e061a+0x8000600020fb (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fffa07ef1fc cls_bpf_classify+0x8000600020dc (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fff81678b68 tc_classify+0x80007f002078 (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fff8164d40b __netif_receive_skb_core+0x80007f0025fb (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fff8164d718 __netif_receive_skb+0x80007f002018 (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fff8164e565 process_backlog+0x80007f002095 (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fff8164dc71 net_rx_action+0x80007f002231 (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fff81767461 __softirqentry_text_start+0x80007f0020d1 (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fff817658ac do_softirq_own_stack+0x80007f00201c (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fff810a2c20 do_softirq+0x80007f002050 (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fff810a2cb5 __local_bh_enable_ip+0x80007f002085 (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fff8168d452 ip_finish_output2+0x80007f002152 (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fff8168ea3d ip_finish_output+0x80007f00217d (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fff8168f2af ip_output+0x80007f00203f (/lib/modules/4.9.0-rc8+/build/vmlinux)
  [...]
  7fff81005854 do_syscall_64+0x80007f002054 (/lib/modules/4.9.0-rc8+/build/vmlinux)
  7fff817649eb return_from_SYSCALL_64+0x80007f002000 (/lib/modules/4.9.0-rc8+/build/vmlinux)
         f5d80 __sendmsg_nocancel+0xffff01c484812007 (/usr/lib64/libc-2.18.so)

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-02-17 13:40:05 -05:00

523 lines
12 KiB
C

/* -*- linux-c -*-
* sysctl_net_core.c: sysctl interface to net core subsystem.
*
* Begun April 1, 1996, Mike Shaver.
* Added /proc/sys/net/core directory entry (empty =) ). [MS]
*/
#include <linux/mm.h>
#include <linux/sysctl.h>
#include <linux/module.h>
#include <linux/socket.h>
#include <linux/netdevice.h>
#include <linux/ratelimit.h>
#include <linux/vmalloc.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/kmemleak.h>
#include <net/ip.h>
#include <net/sock.h>
#include <net/net_ratelimit.h>
#include <net/busy_poll.h>
#include <net/pkt_sched.h>
static int zero = 0;
static int one = 1;
static int min_sndbuf = SOCK_MIN_SNDBUF;
static int min_rcvbuf = SOCK_MIN_RCVBUF;
static int max_skb_frags = MAX_SKB_FRAGS;
static int net_msg_warn; /* Unused, but still a sysctl */
#ifdef CONFIG_RPS
static int rps_sock_flow_sysctl(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
unsigned int orig_size, size;
int ret, i;
struct ctl_table tmp = {
.data = &size,
.maxlen = sizeof(size),
.mode = table->mode
};
struct rps_sock_flow_table *orig_sock_table, *sock_table;
static DEFINE_MUTEX(sock_flow_mutex);
mutex_lock(&sock_flow_mutex);
orig_sock_table = rcu_dereference_protected(rps_sock_flow_table,
lockdep_is_held(&sock_flow_mutex));
size = orig_size = orig_sock_table ? orig_sock_table->mask + 1 : 0;
ret = proc_dointvec(&tmp, write, buffer, lenp, ppos);
if (write) {
if (size) {
if (size > 1<<29) {
/* Enforce limit to prevent overflow */
mutex_unlock(&sock_flow_mutex);
return -EINVAL;
}
size = roundup_pow_of_two(size);
if (size != orig_size) {
sock_table =
vmalloc(RPS_SOCK_FLOW_TABLE_SIZE(size));
if (!sock_table) {
mutex_unlock(&sock_flow_mutex);
return -ENOMEM;
}
rps_cpu_mask = roundup_pow_of_two(nr_cpu_ids) - 1;
sock_table->mask = size - 1;
} else
sock_table = orig_sock_table;
for (i = 0; i < size; i++)
sock_table->ents[i] = RPS_NO_CPU;
} else
sock_table = NULL;
if (sock_table != orig_sock_table) {
rcu_assign_pointer(rps_sock_flow_table, sock_table);
if (sock_table) {
static_key_slow_inc(&rps_needed);
static_key_slow_inc(&rfs_needed);
}
if (orig_sock_table) {
static_key_slow_dec(&rps_needed);
static_key_slow_dec(&rfs_needed);
synchronize_rcu();
vfree(orig_sock_table);
}
}
}
mutex_unlock(&sock_flow_mutex);
return ret;
}
#endif /* CONFIG_RPS */
#ifdef CONFIG_NET_FLOW_LIMIT
static DEFINE_MUTEX(flow_limit_update_mutex);
static int flow_limit_cpu_sysctl(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)
{
struct sd_flow_limit *cur;
struct softnet_data *sd;
cpumask_var_t mask;
int i, len, ret = 0;
if (!alloc_cpumask_var(&mask, GFP_KERNEL))
return -ENOMEM;
if (write) {
ret = cpumask_parse_user(buffer, *lenp, mask);
if (ret)
goto done;
mutex_lock(&flow_limit_update_mutex);
len = sizeof(*cur) + netdev_flow_limit_table_len;
for_each_possible_cpu(i) {
sd = &per_cpu(softnet_data, i);
cur = rcu_dereference_protected(sd->flow_limit,
lockdep_is_held(&flow_limit_update_mutex));
if (cur && !cpumask_test_cpu(i, mask)) {
RCU_INIT_POINTER(sd->flow_limit, NULL);
synchronize_rcu();
kfree(cur);
} else if (!cur && cpumask_test_cpu(i, mask)) {
cur = kzalloc_node(len, GFP_KERNEL,
cpu_to_node(i));
if (!cur) {
/* not unwinding previous changes */
ret = -ENOMEM;
goto write_unlock;
}
cur->num_buckets = netdev_flow_limit_table_len;
rcu_assign_pointer(sd->flow_limit, cur);
}
}
write_unlock:
mutex_unlock(&flow_limit_update_mutex);
} else {
char kbuf[128];
if (*ppos || !*lenp) {
*lenp = 0;
goto done;
}
cpumask_clear(mask);
rcu_read_lock();
for_each_possible_cpu(i) {
sd = &per_cpu(softnet_data, i);
if (rcu_dereference(sd->flow_limit))
cpumask_set_cpu(i, mask);
}
rcu_read_unlock();
len = min(sizeof(kbuf) - 1, *lenp);
len = scnprintf(kbuf, len, "%*pb", cpumask_pr_args(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:
free_cpumask_var(mask);
return ret;
}
static int flow_limit_table_len_sysctl(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)
{
unsigned int old, *ptr;
int ret;
mutex_lock(&flow_limit_update_mutex);
ptr = table->data;
old = *ptr;
ret = proc_dointvec(table, write, buffer, lenp, ppos);
if (!ret && write && !is_power_of_2(*ptr)) {
*ptr = old;
ret = -EINVAL;
}
mutex_unlock(&flow_limit_update_mutex);
return ret;
}
#endif /* CONFIG_NET_FLOW_LIMIT */
#ifdef CONFIG_NET_SCHED
static int set_default_qdisc(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
char id[IFNAMSIZ];
struct ctl_table tbl = {
.data = id,
.maxlen = IFNAMSIZ,
};
int ret;
qdisc_get_default(id, IFNAMSIZ);
ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
if (write && ret == 0)
ret = qdisc_set_default(id);
return ret;
}
#endif
static int proc_do_dev_weight(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
int ret;
ret = proc_dointvec(table, write, buffer, lenp, ppos);
if (ret != 0)
return ret;
dev_rx_weight = weight_p * dev_weight_rx_bias;
dev_tx_weight = weight_p * dev_weight_tx_bias;
return ret;
}
static int proc_do_rss_key(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
struct ctl_table fake_table;
char buf[NETDEV_RSS_KEY_LEN * 3];
snprintf(buf, sizeof(buf), "%*phC", NETDEV_RSS_KEY_LEN, netdev_rss_key);
fake_table.data = buf;
fake_table.maxlen = sizeof(buf);
return proc_dostring(&fake_table, write, buffer, lenp, ppos);
}
static struct ctl_table net_core_table[] = {
#ifdef CONFIG_NET
{
.procname = "wmem_max",
.data = &sysctl_wmem_max,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &min_sndbuf,
},
{
.procname = "rmem_max",
.data = &sysctl_rmem_max,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &min_rcvbuf,
},
{
.procname = "wmem_default",
.data = &sysctl_wmem_default,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &min_sndbuf,
},
{
.procname = "rmem_default",
.data = &sysctl_rmem_default,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &min_rcvbuf,
},
{
.procname = "dev_weight",
.data = &weight_p,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_do_dev_weight,
},
{
.procname = "dev_weight_rx_bias",
.data = &dev_weight_rx_bias,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_do_dev_weight,
},
{
.procname = "dev_weight_tx_bias",
.data = &dev_weight_tx_bias,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_do_dev_weight,
},
{
.procname = "netdev_max_backlog",
.data = &netdev_max_backlog,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec
},
{
.procname = "netdev_rss_key",
.data = &netdev_rss_key,
.maxlen = sizeof(int),
.mode = 0444,
.proc_handler = proc_do_rss_key,
},
#ifdef CONFIG_BPF_JIT
{
.procname = "bpf_jit_enable",
.data = &bpf_jit_enable,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec
},
# ifdef CONFIG_HAVE_EBPF_JIT
{
.procname = "bpf_jit_harden",
.data = &bpf_jit_harden,
.maxlen = sizeof(int),
.mode = 0600,
.proc_handler = proc_dointvec,
},
{
.procname = "bpf_jit_kallsyms",
.data = &bpf_jit_kallsyms,
.maxlen = sizeof(int),
.mode = 0600,
.proc_handler = proc_dointvec,
},
# endif
#endif
{
.procname = "netdev_tstamp_prequeue",
.data = &netdev_tstamp_prequeue,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec
},
{
.procname = "message_cost",
.data = &net_ratelimit_state.interval,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_jiffies,
},
{
.procname = "message_burst",
.data = &net_ratelimit_state.burst,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{
.procname = "optmem_max",
.data = &sysctl_optmem_max,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec
},
{
.procname = "tstamp_allow_data",
.data = &sysctl_tstamp_allow_data,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &zero,
.extra2 = &one
},
#ifdef CONFIG_RPS
{
.procname = "rps_sock_flow_entries",
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = rps_sock_flow_sysctl
},
#endif
#ifdef CONFIG_NET_FLOW_LIMIT
{
.procname = "flow_limit_cpu_bitmap",
.mode = 0644,
.proc_handler = flow_limit_cpu_sysctl
},
{
.procname = "flow_limit_table_len",
.data = &netdev_flow_limit_table_len,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = flow_limit_table_len_sysctl
},
#endif /* CONFIG_NET_FLOW_LIMIT */
#ifdef CONFIG_NET_RX_BUSY_POLL
{
.procname = "busy_poll",
.data = &sysctl_net_busy_poll,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec
},
{
.procname = "busy_read",
.data = &sysctl_net_busy_read,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec
},
#endif
#ifdef CONFIG_NET_SCHED
{
.procname = "default_qdisc",
.mode = 0644,
.maxlen = IFNAMSIZ,
.proc_handler = set_default_qdisc
},
#endif
#endif /* CONFIG_NET */
{
.procname = "netdev_budget",
.data = &netdev_budget,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec
},
{
.procname = "warnings",
.data = &net_msg_warn,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec
},
{
.procname = "max_skb_frags",
.data = &sysctl_max_skb_frags,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &one,
.extra2 = &max_skb_frags,
},
{ }
};
static struct ctl_table netns_core_table[] = {
{
.procname = "somaxconn",
.data = &init_net.core.sysctl_somaxconn,
.maxlen = sizeof(int),
.mode = 0644,
.extra1 = &zero,
.proc_handler = proc_dointvec_minmax
},
{ }
};
static __net_init int sysctl_core_net_init(struct net *net)
{
struct ctl_table *tbl;
net->core.sysctl_somaxconn = SOMAXCONN;
tbl = netns_core_table;
if (!net_eq(net, &init_net)) {
tbl = kmemdup(tbl, sizeof(netns_core_table), GFP_KERNEL);
if (tbl == NULL)
goto err_dup;
tbl[0].data = &net->core.sysctl_somaxconn;
/* Don't export any sysctls to unprivileged users */
if (net->user_ns != &init_user_ns) {
tbl[0].procname = NULL;
}
}
net->core.sysctl_hdr = register_net_sysctl(net, "net/core", tbl);
if (net->core.sysctl_hdr == NULL)
goto err_reg;
return 0;
err_reg:
if (tbl != netns_core_table)
kfree(tbl);
err_dup:
return -ENOMEM;
}
static __net_exit void sysctl_core_net_exit(struct net *net)
{
struct ctl_table *tbl;
tbl = net->core.sysctl_hdr->ctl_table_arg;
unregister_net_sysctl_table(net->core.sysctl_hdr);
BUG_ON(tbl == netns_core_table);
kfree(tbl);
}
static __net_initdata struct pernet_operations sysctl_core_ops = {
.init = sysctl_core_net_init,
.exit = sysctl_core_net_exit,
};
static __init int sysctl_core_init(void)
{
register_net_sysctl(&init_net, "net/core", net_core_table);
return register_pernet_subsys(&sysctl_core_ops);
}
fs_initcall(sysctl_core_init);