linux/net/core/sysctl_net_core.c
Alexei Starovoitov 290af86629 bpf: introduce BPF_JIT_ALWAYS_ON config
The BPF interpreter has been used as part of the spectre 2 attack CVE-2017-5715.

A quote from goolge project zero blog:
"At this point, it would normally be necessary to locate gadgets in
the host kernel code that can be used to actually leak data by reading
from an attacker-controlled location, shifting and masking the result
appropriately and then using the result of that as offset to an
attacker-controlled address for a load. But piecing gadgets together
and figuring out which ones work in a speculation context seems annoying.
So instead, we decided to use the eBPF interpreter, which is built into
the host kernel - while there is no legitimate way to invoke it from inside
a VM, the presence of the code in the host kernel's text section is sufficient
to make it usable for the attack, just like with ordinary ROP gadgets."

To make attacker job harder introduce BPF_JIT_ALWAYS_ON config
option that removes interpreter from the kernel in favor of JIT-only mode.
So far eBPF JIT is supported by:
x64, arm64, arm32, sparc64, s390, powerpc64, mips64

The start of JITed program is randomized and code page is marked as read-only.
In addition "constant blinding" can be turned on with net.core.bpf_jit_harden

v2->v3:
- move __bpf_prog_ret0 under ifdef (Daniel)

v1->v2:
- fix init order, test_bpf and cBPF (Daniel's feedback)
- fix offloaded bpf (Jakub's feedback)
- add 'return 0' dummy in case something can invoke prog->bpf_func
- retarget bpf tree. For bpf-next the patch would need one extra hunk.
  It will be sent when the trees are merged back to net-next

Considered doing:
  int bpf_jit_enable __read_mostly = BPF_EBPF_JIT_DEFAULT;
but it seems better to land the patch as-is and in bpf-next remove
bpf_jit_enable global variable from all JITs, consolidate in one place
and remove this jit_init() function.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
2018-01-09 22:25:26 +01:00

538 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0
/* -*- 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,
#ifndef CONFIG_BPF_JIT_ALWAYS_ON
.proc_handler = proc_dointvec
#else
.proc_handler = proc_dointvec_minmax,
.extra1 = &one,
.extra2 = &one,
#endif
},
# 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_minmax,
.extra1 = &zero,
},
{
.procname = "busy_read",
.data = &sysctl_net_busy_read,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &zero,
},
#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,
},
{
.procname = "netdev_budget_usecs",
.data = &netdev_budget_usecs,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = &zero,
},
{ }
};
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;
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);