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|
/*
* 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 <linux/gfp.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/uaccess.h>
#include <asm/unaligned.h>
#include <linux/filter.h>
#include <linux/reciprocal_div.h>
#include <linux/ratelimit.h>
/* No hurry in this branch
*
* Exported for the bpf jit load helper.
*/
void *bpf_internal_load_pointer_neg_helper(const struct sk_buff *skb, int k, unsigned int size)
{
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 + size <= skb_tail_pointer(skb))
return ptr;
return NULL;
}
static inline void *load_pointer(const struct sk_buff *skb, int k,
unsigned int size, void *buffer)
{
if (k >= 0)
return skb_header_pointer(skb, k, size, buffer);
return bpf_internal_load_pointer_neg_helper(skb, k, size);
}
/**
* 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();
filter = rcu_dereference(sk->sk_filter);
if (filter) {
unsigned int pkt_len = SK_RUN_FILTER(filter, skb);
err = pkt_len ? pskb_trim(skb, pkt_len) : -EPERM;
}
rcu_read_unlock();
return err;
}
EXPORT_SYMBOL(sk_filter);
/**
* sk_run_filter - run a filter on a socket
* @skb: buffer to run the filter on
* @fentry: filter to apply
*
* 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.
* Because all jumps are guaranteed to be before last instruction,
* and last instruction guaranteed to be a RET, we dont need to check
* flen. (We used to pass to this function the length of filter)
*/
unsigned int sk_run_filter(const struct sk_buff *skb,
const struct sock_filter *fentry)
{
void *ptr;
u32 A = 0; /* Accumulator */
u32 X = 0; /* Index Register */
u32 mem[BPF_MEMWORDS]; /* Scratch Memory Store */
u32 tmp;
int k;
/*
* Process array of filter instructions.
*/
for (;; fentry++) {
#if defined(CONFIG_X86_32)
#define K (fentry->k)
#else
const u32 K = fentry->k;
#endif
switch (fentry->code) {
case BPF_S_ALU_ADD_X:
A += X;
continue;
case BPF_S_ALU_ADD_K:
A += K;
continue;
case BPF_S_ALU_SUB_X:
A -= X;
continue;
case BPF_S_ALU_SUB_K:
A -= K;
continue;
case BPF_S_ALU_MUL_X:
A *= X;
continue;
case BPF_S_ALU_MUL_K:
A *= K;
continue;
case BPF_S_ALU_DIV_X:
if (X == 0)
return 0;
A /= X;
continue;
case BPF_S_ALU_DIV_K:
A = reciprocal_divide(A, K);
continue;
case BPF_S_ALU_AND_X:
A &= X;
continue;
case BPF_S_ALU_AND_K:
A &= K;
continue;
case BPF_S_ALU_OR_X:
A |= X;
continue;
case BPF_S_ALU_OR_K:
A |= K;
continue;
case BPF_S_ALU_LSH_X:
A <<= X;
continue;
case BPF_S_ALU_LSH_K:
A <<= K;
continue;
case BPF_S_ALU_RSH_X:
A >>= X;
continue;
case BPF_S_ALU_RSH_K:
A >>= K;
continue;
case BPF_S_ALU_NEG:
A = -A;
continue;
case BPF_S_JMP_JA:
fentry += K;
continue;
case BPF_S_JMP_JGT_K:
fentry += (A > K) ? fentry->jt : fentry->jf;
continue;
case BPF_S_JMP_JGE_K:
fentry += (A >= K) ? fentry->jt : fentry->jf;
continue;
case BPF_S_JMP_JEQ_K:
fentry += (A == K) ? fentry->jt : fentry->jf;
continue;
case BPF_S_JMP_JSET_K:
fentry += (A & K) ? fentry->jt : fentry->jf;
continue;
case BPF_S_JMP_JGT_X:
fentry += (A > X) ? fentry->jt : fentry->jf;
continue;
case BPF_S_JMP_JGE_X:
fentry += (A >= X) ? fentry->jt : fentry->jf;
continue;
case BPF_S_JMP_JEQ_X:
fentry += (A == X) ? fentry->jt : fentry->jf;
continue;
case BPF_S_JMP_JSET_X:
fentry += (A & X) ? fentry->jt : fentry->jf;
continue;
case BPF_S_LD_W_ABS:
k = K;
load_w:
ptr = load_pointer(skb, k, 4, &tmp);
if (ptr != NULL) {
A = get_unaligned_be32(ptr);
continue;
}
return 0;
case BPF_S_LD_H_ABS:
k = K;
load_h:
ptr = load_pointer(skb, k, 2, &tmp);
if (ptr != NULL) {
A = get_unaligned_be16(ptr);
continue;
}
return 0;
case BPF_S_LD_B_ABS
|