/* [<][>][^][v][top][bottom][index][help] */
DEFINITIONS
This source file includes following definitions.
- __load_pointer
- load_pointer
- sk_filter
- sk_run_filter
- sk_chk_filter
- sk_filter_rcu_release
- sk_filter_delayed_uncharge
- sk_attach_filter
- sk_detach_filter
/*
* Linux Socket Filter - Kernel level socket filtering
*
* Author:
* Jay Schulist <jschlst@samba.org>
*
* Based on the design of:
* - The Berkeley Packet Filter
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Andi Kleen - Fix a few bad bugs and races.
* Kris Katterjohn - Added many additional checks in sk_chk_filter()
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/fcntl.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/if_packet.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/netlink.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <linux/errno.h>
#include <linux/timer.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/unaligned.h>
#include <linux/filter.h>
/* No hurry in this branch */
static void *__load_pointer(struct sk_buff *skb, int k)
{
u8 *ptr = NULL;
if (k >= SKF_NET_OFF)
ptr = skb_network_header(skb) + k - SKF_NET_OFF;
else if (k >= SKF_LL_OFF)
ptr = skb_mac_header(skb) + k - SKF_LL_OFF;
if (ptr >= skb->head && ptr < skb_tail_pointer(skb))
return ptr;
return NULL;
}
static inline void *load_pointer(struct sk_buff *skb, int k,
unsigned int size, void *buffer)
{
if (k >= 0)
return skb_header_pointer(skb, k, size, buffer);
else {
if (k >= SKF_AD_OFF)
return NULL;
return __load_pointer(skb, k);
}
}
/**
* sk_filter - run a packet through a socket filter
* @sk: sock associated with &sk_buff
* @skb: buffer to filter
*
* Run the filter code and then cut skb->data to correct size returned by
* sk_run_filter. If pkt_len is 0 we toss packet. If skb->len is smaller
* than pkt_len we keep whole skb->data. This is the socket level
* wrapper to sk_run_filter. It returns 0 if the packet should
* be accepted or -EPERM if the packet should be tossed.
*
*/
int sk_filter(struct sock *sk, struct sk_buff *skb)
{
int err;
struct sk_filter *filter;
err = security_sock_rcv_skb(sk, skb);
if (err)
return err;
rcu_read_lock_bh();
filter = rcu_dereference(sk->sk_filter);
if (filter) {
unsigned int pkt_len = sk_run_filter(skb, filter->insns,
filter->len);
err = pkt_len ? pskb_trim(skb, pkt_len) : -EPERM;
}
rcu_read_unlock_bh();
return err;
}
EXPORT_SYMBOL(sk_filter);
/**
* sk_run_filter - run a filter on a socket
* @skb: buffer to run the filter on
* @filter: filter to apply
* @flen: length of filter
*
* Decode and apply filter instructions to the skb->data.
* Return length to keep, 0 for none. skb is the data we are
* filtering, filter is the array of filter instructions, and
* len is the number of filter blocks in the array.
*/
unsigned int sk_run_filter(struct sk_buff *skb, struct sock_filter *filter, int flen)
{
struct sock_filter *fentry; /* We walk down these */
void *ptr;
u32 A = 0; /* Accumulator */
u32 X = 0; /* Index Register */
u32 mem[BPF_MEMWORDS]; /* Scratch Memory Store */
u32 tmp;
int k;
int pc;
/*
* Process array of filter instructions.
*/
for (pc = 0; pc < flen; pc++) {
fentry = &filter[pc];
switch (fentry->code) {
case BPF_ALU|BPF_ADD|BPF_X:
A += X;
continue;
case BPF_ALU|BPF_ADD|BPF_K:
A += fentry->k;
continue;
case BPF_ALU|BPF_SUB|BPF_X:
A -= X;
continue;
case BPF_ALU|BPF_SUB|BPF_K:
A -= fentry->k;
continue;
case BPF_ALU|BPF_MUL|BPF_X:
A *= X;
continue;
case BPF_ALU|BPF_MUL|BPF_K:
A *= fentry->k;
continue;
case BPF_ALU|BPF_DIV|BPF_X:
if (X == 0)
return 0;
A /= X;
continue;
case BPF_ALU|BPF_DIV|BPF_K:
A /= fentry->k;
continue;
case BPF_ALU|BPF_AND|BPF_X:
A &= X;
continue;
case BPF_ALU|BPF_AND|BPF_K:
A &= fentry->k;
continue;
case BPF_ALU|BPF_OR|BPF_X:
A |= X;
continue;
case BPF_ALU|BPF_OR|BPF_K:
A |= fentry->k;
continue;
case BPF_ALU|BPF_LSH|BPF_X:
A <<= X;
continue;
case BPF_ALU|BPF_LSH|BPF_K:
A <<= fentry->k;
continue;
case BPF_ALU|BPF_RSH|BPF_X:
A >>= X;
continue;
case BPF_ALU|BPF_RSH|BPF_K:
A >>= fentry->k;
continue;
case BPF_ALU|BPF_NEG:
A = -A;
continue;
case BPF_JMP|BPF_JA:
pc += fentry->k;
continue;
case BPF_JMP|BPF_JGT|BPF_K:
pc += (A > fentry->k) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JGE|BPF_K:
pc += (A >= fentry->k) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JEQ|BPF_K:
pc += (A == fentry->k) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JSET|BPF_K:
pc += (A & fentry->k) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JGT|BPF_X:
pc += (A > X) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JGE|BPF_X:
pc += (A >= X) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JEQ|BPF_X:
pc += (A == X) ? fentry->jt : fentry->jf;
continue;
case BPF_JMP|BPF_JSET|BPF_X:
pc += (A & X) ? fentry->jt : fentry->jf;
continue;
case BPF_LD|BPF_W|BPF_ABS:
k = fentry->k;
load_w:
ptr = load_pointer(skb, k, 4, &tmp);
if (ptr != NULL) {
A = get_unaligned_be32(ptr);
continue;
}
break;
case BPF_LD|BPF_H|BPF_ABS:
k = fentry->k;
load_h:
ptr = load_pointer(skb, k, 2, &tmp);
if (ptr != NULL) {
A = get_unaligned_be16(ptr);
continue;
}
break;
case BPF_LD|BPF_B|BPF_ABS:
k = fentry->k;
load_b:
ptr = load_pointer(skb, k, 1, &tmp);
if (ptr != NULL) {
A = *(u8 *)ptr;
continue;
}
break;
case BPF_LD|BPF_W|BPF_LEN:
A = skb->len;
continue;
case BPF_LDX|BPF_W|BPF_LEN:
X = skb->len;
continue;
case BPF_LD|BPF_W|BPF_IND:
k = X + fentry->k;
goto load_w;
case BPF_LD|BPF_H|BPF_IND:
k = X + fentry->k;
goto load_h;
case BPF_LD|BPF_B|BPF_IND:
k = X + fentry->k;
goto load_b;
case BPF_LDX|BPF_B|BPF_MSH:
ptr = load_pointer(skb, fentry->k, 1, &tmp);
if (ptr != NULL) {
X = (*(u8 *)ptr & 0xf) << 2;
continue;
}
return 0;
case BPF_LD|BPF_IMM:
A = fentry->k;
continue;
case BPF_LDX|BPF_IMM:
X = fentry->k;
continue;
case BPF_LD|BPF_MEM:
A = mem[fentry->k];
continue;
case BPF_LDX|BPF_MEM:
X = mem[fentry->k];
continue;
case BPF_MISC|BPF_TAX:
X = A;
continue;
case BPF_MISC|BPF_TXA:
A = X;
continue;
case BPF_RET|BPF_K:
return fentry->k;
case BPF_RET|BPF_A:
return A;
case BPF_ST:
mem[fentry->k] = A;
continue;
case BPF_STX:
mem[fentry->k] = X;
continue;
default:
WARN_ON(1);
return 0;
}
/*
* Handle ancillary data, which are impossible
* (or very difficult) to get parsing packet contents.
*/
switch (k-SKF_AD_OFF) {
case SKF_AD_PROTOCOL:
A = ntohs(skb->protocol);
continue;
case SKF_AD_PKTTYPE:
A = skb->pkt_type;
continue;
case SKF_AD_IFINDEX:
A = skb->dev->ifindex;
continue;
case SKF_AD_NLATTR: {
struct nlattr *nla;
if (skb_is_nonlinear(skb))
return 0;
if (A > skb->len - sizeof(struct nlattr))
return 0;
nla = nla_find((struct nlattr *)&skb->data[A],
skb->len - A, X);
if (nla)
A = (void *)nla - (void *)skb->data;
else
A = 0;
continue;
}
default:
return 0;
}
}
return 0;
}
EXPORT_SYMBOL(sk_run_filter);
/**
* sk_chk_filter - verify socket filter code
* @filter: filter to verify
* @flen: length of filter
*
* Check the user's filter code. If we let some ugly
* filter code slip through kaboom! The filter must contain
* no references or jumps that are out of range, no illegal
* instructions, and must end with a RET instruction.
*
* All jumps are forward as they are not signed.
*
* Returns 0 if the rule set is legal or -EINVAL if not.
*/
int sk_chk_filter(struct sock_filter *filter, int flen)
{
struct sock_filter *ftest;
int pc;
if (flen == 0 || flen > BPF_MAXINSNS)
return -EINVAL;
/* check the filter code now */
for (pc = 0; pc < flen; pc++) {
ftest = &filter[pc];
/* Only allow valid instructions */
switch (ftest->code) {
case BPF_ALU|BPF_ADD|BPF_K:
case BPF_ALU|BPF_ADD|BPF_X:
case BPF_ALU|BPF_SUB|BPF_K:
case BPF_ALU|BPF_SUB|BPF_X:
case BPF_ALU|BPF_MUL|BPF_K:
case BPF_ALU|BPF_MUL|BPF_X:
case BPF_ALU|BPF_DIV|BPF_X:
case BPF_ALU|BPF_AND|BPF_K:
case BPF_ALU|BPF_AND|BPF_X:
case BPF_ALU|BPF_OR|BPF_K:
case BPF_ALU|BPF_OR|BPF_X:
case BPF_ALU|BPF_LSH|BPF_K:
case BPF_ALU|BPF_LSH|BPF_X:
case BPF_ALU|BPF_RSH|BPF_K:
case BPF_ALU|BPF_RSH|BPF_X:
case BPF_ALU|BPF_NEG:
case BPF_LD|BPF_W|BPF_ABS:
case BPF_LD|BPF_H|BPF_ABS:
case BPF_LD|BPF_B|BPF_ABS:
case BPF_LD|BPF_W|BPF_LEN:
case BPF_LD|BPF_W|BPF_IND:
case BPF_LD|BPF_H|BPF_IND:
case BPF_LD|BPF_B|BPF_IND:
case BPF_LD|BPF_IMM:
case BPF_LDX|BPF_W|BPF_LEN:
case BPF_LDX|BPF_B|BPF_MSH:
case BPF_LDX|BPF_IMM:
case BPF_MISC|BPF_TAX:
case BPF_MISC|BPF_TXA:
case BPF_RET|BPF_K:
case BPF_RET|BPF_A:
break;
/* Some instructions need special checks */
case BPF_ALU|BPF_DIV|BPF_K:
/* check for division by zero */
if (ftest->k == 0)
return -EINVAL;
break;
case BPF_LD|BPF_MEM:
case BPF_LDX|BPF_MEM:
case BPF_ST:
case BPF_STX:
/* check for invalid memory addresses */
if (ftest->k >= BPF_MEMWORDS)
return -EINVAL;
break;
case BPF_JMP|BPF_JA:
/*
* Note, the large ftest->k might cause loops.
* Compare this with conditional jumps below,
* where offsets are limited. --ANK (981016)
*/
if (ftest->k >= (unsigned)(flen-pc-1))
return -EINVAL;
break;
case BPF_JMP|BPF_JEQ|BPF_K:
case BPF_JMP|BPF_JEQ|BPF_X:
case BPF_JMP|BPF_JGE|BPF_K:
case BPF_JMP|BPF_JGE|BPF_X:
case BPF_JMP|BPF_JGT|BPF_K:
case BPF_JMP|BPF_JGT|BPF_X:
case BPF_JMP|BPF_JSET|BPF_K:
case BPF_JMP|BPF_JSET|BPF_X:
/* for conditionals both must be safe */
if (pc + ftest->jt + 1 >= flen ||
pc + ftest->jf + 1 >= flen)
return -EINVAL;
break;
default:
return -EINVAL;
}
}
return (BPF_CLASS(filter[flen - 1].code) == BPF_RET) ? 0 : -EINVAL;
}
EXPORT_SYMBOL(sk_chk_filter);
/**
* sk_filter_rcu_release: Release a socket filter by rcu_head
* @rcu: rcu_head that contains the sk_filter to free
*/
static void sk_filter_rcu_release(struct rcu_head *rcu)
{
struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);
sk_filter_release(fp);
}
static void sk_filter_delayed_uncharge(struct sock *sk, struct sk_filter *fp)
{
unsigned int size = sk_filter_len(fp);
atomic_sub(size, &sk->sk_omem_alloc);
call_rcu_bh(&fp->rcu, sk_filter_rcu_release);
}
/**
* sk_attach_filter - attach a socket filter
* @fprog: the filter program
* @sk: the socket to use
*
* Attach the user's filter code. We first run some sanity checks on
* it to make sure it does not explode on us later. If an error
* occurs or there is insufficient memory for the filter a negative
* errno code is returned. On success the return is zero.
*/
int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
{
struct sk_filter *fp, *old_fp;
unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
int err;
/* Make sure new filter is there and in the right amounts. */
if (fprog->filter == NULL)
return -EINVAL;
fp = sock_kmalloc(sk, fsize+sizeof(*fp), GFP_KERNEL);
if (!fp)
return -ENOMEM;
if (copy_from_user(fp->insns, fprog->filter, fsize)) {
sock_kfree_s(sk, fp, fsize+sizeof(*fp));
return -EFAULT;
}
atomic_set(&fp->refcnt, 1);
fp->len = fprog->len;
err = sk_chk_filter(fp->insns, fp->len);
if (err) {
sk_filter_uncharge(sk, fp);
return err;
}
rcu_read_lock_bh();
old_fp = rcu_dereference(sk->sk_filter);
rcu_assign_pointer(sk->sk_filter, fp);
rcu_read_unlock_bh();
if (old_fp)
sk_filter_delayed_uncharge(sk, old_fp);
return 0;
}
int sk_detach_filter(struct sock *sk)
{
int ret = -ENOENT;
struct sk_filter *filter;
rcu_read_lock_bh();
filter = rcu_dereference(sk->sk_filter);
if (filter) {
rcu_assign_pointer(sk->sk_filter, NULL);
sk_filter_delayed_uncharge(sk, filter);
ret = 0;
}
rcu_read_unlock_bh();
return ret;
}