d3e2ce3bcd
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
524 lines
12 KiB
C
524 lines
12 KiB
C
/*
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* Linux Socket Filter - Kernel level socket filtering
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*
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* Author:
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* Jay Schulist <jschlst@samba.org>
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*
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* Based on the design of:
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* - The Berkeley Packet Filter
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Andi Kleen - Fix a few bad bugs and races.
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* Kris Katterjohn - Added many additional checks in sk_chk_filter()
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*/
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/mm.h>
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#include <linux/fcntl.h>
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#include <linux/socket.h>
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#include <linux/in.h>
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#include <linux/inet.h>
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#include <linux/netdevice.h>
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#include <linux/if_packet.h>
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#include <net/ip.h>
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#include <net/protocol.h>
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#include <net/netlink.h>
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#include <linux/skbuff.h>
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#include <net/sock.h>
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#include <linux/errno.h>
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#include <linux/timer.h>
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#include <asm/system.h>
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#include <asm/uaccess.h>
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#include <asm/unaligned.h>
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#include <linux/filter.h>
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/* No hurry in this branch */
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static void *__load_pointer(struct sk_buff *skb, int k)
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{
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u8 *ptr = NULL;
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if (k >= SKF_NET_OFF)
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ptr = skb_network_header(skb) + k - SKF_NET_OFF;
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else if (k >= SKF_LL_OFF)
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ptr = skb_mac_header(skb) + k - SKF_LL_OFF;
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if (ptr >= skb->head && ptr < skb_tail_pointer(skb))
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return ptr;
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return NULL;
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}
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static inline void *load_pointer(struct sk_buff *skb, int k,
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unsigned int size, void *buffer)
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{
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if (k >= 0)
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return skb_header_pointer(skb, k, size, buffer);
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else {
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if (k >= SKF_AD_OFF)
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return NULL;
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return __load_pointer(skb, k);
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}
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}
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/**
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* sk_filter - run a packet through a socket filter
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* @sk: sock associated with &sk_buff
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* @skb: buffer to filter
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* @needlock: set to 1 if the sock is not locked by caller.
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*
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* Run the filter code and then cut skb->data to correct size returned by
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* sk_run_filter. If pkt_len is 0 we toss packet. If skb->len is smaller
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* than pkt_len we keep whole skb->data. This is the socket level
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* wrapper to sk_run_filter. It returns 0 if the packet should
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* be accepted or -EPERM if the packet should be tossed.
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*
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*/
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int sk_filter(struct sock *sk, struct sk_buff *skb)
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{
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int err;
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struct sk_filter *filter;
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err = security_sock_rcv_skb(sk, skb);
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if (err)
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return err;
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rcu_read_lock_bh();
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filter = rcu_dereference(sk->sk_filter);
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if (filter) {
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unsigned int pkt_len = sk_run_filter(skb, filter->insns,
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filter->len);
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err = pkt_len ? pskb_trim(skb, pkt_len) : -EPERM;
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}
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rcu_read_unlock_bh();
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return err;
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}
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EXPORT_SYMBOL(sk_filter);
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/**
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* sk_run_filter - run a filter on a socket
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* @skb: buffer to run the filter on
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* @filter: filter to apply
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* @flen: length of filter
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*
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* Decode and apply filter instructions to the skb->data.
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* Return length to keep, 0 for none. skb is the data we are
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* filtering, filter is the array of filter instructions, and
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* len is the number of filter blocks in the array.
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*/
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unsigned int sk_run_filter(struct sk_buff *skb, struct sock_filter *filter, int flen)
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{
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struct sock_filter *fentry; /* We walk down these */
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void *ptr;
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u32 A = 0; /* Accumulator */
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u32 X = 0; /* Index Register */
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u32 mem[BPF_MEMWORDS]; /* Scratch Memory Store */
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u32 tmp;
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int k;
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int pc;
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/*
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* Process array of filter instructions.
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*/
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for (pc = 0; pc < flen; pc++) {
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fentry = &filter[pc];
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switch (fentry->code) {
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case BPF_ALU|BPF_ADD|BPF_X:
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A += X;
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continue;
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case BPF_ALU|BPF_ADD|BPF_K:
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A += fentry->k;
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continue;
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case BPF_ALU|BPF_SUB|BPF_X:
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A -= X;
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continue;
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case BPF_ALU|BPF_SUB|BPF_K:
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A -= fentry->k;
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continue;
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case BPF_ALU|BPF_MUL|BPF_X:
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A *= X;
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continue;
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case BPF_ALU|BPF_MUL|BPF_K:
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A *= fentry->k;
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continue;
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case BPF_ALU|BPF_DIV|BPF_X:
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if (X == 0)
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return 0;
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A /= X;
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continue;
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case BPF_ALU|BPF_DIV|BPF_K:
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A /= fentry->k;
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continue;
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case BPF_ALU|BPF_AND|BPF_X:
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A &= X;
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continue;
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case BPF_ALU|BPF_AND|BPF_K:
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A &= fentry->k;
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continue;
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case BPF_ALU|BPF_OR|BPF_X:
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A |= X;
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continue;
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case BPF_ALU|BPF_OR|BPF_K:
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A |= fentry->k;
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continue;
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case BPF_ALU|BPF_LSH|BPF_X:
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A <<= X;
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continue;
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case BPF_ALU|BPF_LSH|BPF_K:
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A <<= fentry->k;
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continue;
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case BPF_ALU|BPF_RSH|BPF_X:
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A >>= X;
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continue;
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case BPF_ALU|BPF_RSH|BPF_K:
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A >>= fentry->k;
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continue;
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case BPF_ALU|BPF_NEG:
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A = -A;
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continue;
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case BPF_JMP|BPF_JA:
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pc += fentry->k;
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continue;
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case BPF_JMP|BPF_JGT|BPF_K:
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pc += (A > fentry->k) ? fentry->jt : fentry->jf;
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continue;
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case BPF_JMP|BPF_JGE|BPF_K:
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pc += (A >= fentry->k) ? fentry->jt : fentry->jf;
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continue;
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case BPF_JMP|BPF_JEQ|BPF_K:
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pc += (A == fentry->k) ? fentry->jt : fentry->jf;
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continue;
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case BPF_JMP|BPF_JSET|BPF_K:
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pc += (A & fentry->k) ? fentry->jt : fentry->jf;
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continue;
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case BPF_JMP|BPF_JGT|BPF_X:
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pc += (A > X) ? fentry->jt : fentry->jf;
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continue;
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case BPF_JMP|BPF_JGE|BPF_X:
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pc += (A >= X) ? fentry->jt : fentry->jf;
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continue;
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case BPF_JMP|BPF_JEQ|BPF_X:
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pc += (A == X) ? fentry->jt : fentry->jf;
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continue;
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case BPF_JMP|BPF_JSET|BPF_X:
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pc += (A & X) ? fentry->jt : fentry->jf;
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continue;
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case BPF_LD|BPF_W|BPF_ABS:
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k = fentry->k;
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load_w:
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ptr = load_pointer(skb, k, 4, &tmp);
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if (ptr != NULL) {
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A = get_unaligned_be32(ptr);
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continue;
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}
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break;
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case BPF_LD|BPF_H|BPF_ABS:
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k = fentry->k;
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load_h:
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ptr = load_pointer(skb, k, 2, &tmp);
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if (ptr != NULL) {
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A = get_unaligned_be16(ptr);
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continue;
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}
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break;
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case BPF_LD|BPF_B|BPF_ABS:
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k = fentry->k;
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load_b:
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ptr = load_pointer(skb, k, 1, &tmp);
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if (ptr != NULL) {
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A = *(u8 *)ptr;
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continue;
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}
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break;
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case BPF_LD|BPF_W|BPF_LEN:
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A = skb->len;
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continue;
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case BPF_LDX|BPF_W|BPF_LEN:
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X = skb->len;
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continue;
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case BPF_LD|BPF_W|BPF_IND:
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k = X + fentry->k;
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goto load_w;
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case BPF_LD|BPF_H|BPF_IND:
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k = X + fentry->k;
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goto load_h;
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case BPF_LD|BPF_B|BPF_IND:
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k = X + fentry->k;
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goto load_b;
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case BPF_LDX|BPF_B|BPF_MSH:
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ptr = load_pointer(skb, fentry->k, 1, &tmp);
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if (ptr != NULL) {
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X = (*(u8 *)ptr & 0xf) << 2;
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continue;
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}
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return 0;
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case BPF_LD|BPF_IMM:
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A = fentry->k;
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continue;
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case BPF_LDX|BPF_IMM:
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X = fentry->k;
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continue;
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case BPF_LD|BPF_MEM:
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A = mem[fentry->k];
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continue;
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case BPF_LDX|BPF_MEM:
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X = mem[fentry->k];
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continue;
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case BPF_MISC|BPF_TAX:
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X = A;
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continue;
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case BPF_MISC|BPF_TXA:
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A = X;
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continue;
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case BPF_RET|BPF_K:
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return fentry->k;
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case BPF_RET|BPF_A:
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return A;
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case BPF_ST:
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mem[fentry->k] = A;
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continue;
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case BPF_STX:
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mem[fentry->k] = X;
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continue;
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default:
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WARN_ON(1);
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return 0;
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}
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/*
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* Handle ancillary data, which are impossible
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* (or very difficult) to get parsing packet contents.
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*/
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switch (k-SKF_AD_OFF) {
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case SKF_AD_PROTOCOL:
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A = ntohs(skb->protocol);
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continue;
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case SKF_AD_PKTTYPE:
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A = skb->pkt_type;
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continue;
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case SKF_AD_IFINDEX:
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A = skb->dev->ifindex;
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continue;
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case SKF_AD_NLATTR: {
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struct nlattr *nla;
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if (skb_is_nonlinear(skb))
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return 0;
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if (A > skb->len - sizeof(struct nlattr))
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return 0;
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nla = nla_find((struct nlattr *)&skb->data[A],
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skb->len - A, X);
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if (nla)
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A = (void *)nla - (void *)skb->data;
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else
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A = 0;
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continue;
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}
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default:
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return 0;
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}
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}
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return 0;
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}
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EXPORT_SYMBOL(sk_run_filter);
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/**
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* sk_chk_filter - verify socket filter code
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* @filter: filter to verify
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* @flen: length of filter
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*
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* Check the user's filter code. If we let some ugly
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* filter code slip through kaboom! The filter must contain
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* no references or jumps that are out of range, no illegal
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* instructions, and must end with a RET instruction.
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*
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* All jumps are forward as they are not signed.
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*
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* Returns 0 if the rule set is legal or -EINVAL if not.
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*/
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int sk_chk_filter(struct sock_filter *filter, int flen)
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{
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struct sock_filter *ftest;
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int pc;
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if (flen == 0 || flen > BPF_MAXINSNS)
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return -EINVAL;
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/* check the filter code now */
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for (pc = 0; pc < flen; pc++) {
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ftest = &filter[pc];
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/* Only allow valid instructions */
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switch (ftest->code) {
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case BPF_ALU|BPF_ADD|BPF_K:
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case BPF_ALU|BPF_ADD|BPF_X:
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case BPF_ALU|BPF_SUB|BPF_K:
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case BPF_ALU|BPF_SUB|BPF_X:
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case BPF_ALU|BPF_MUL|BPF_K:
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case BPF_ALU|BPF_MUL|BPF_X:
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case BPF_ALU|BPF_DIV|BPF_X:
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case BPF_ALU|BPF_AND|BPF_K:
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case BPF_ALU|BPF_AND|BPF_X:
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case BPF_ALU|BPF_OR|BPF_K:
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case BPF_ALU|BPF_OR|BPF_X:
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case BPF_ALU|BPF_LSH|BPF_K:
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case BPF_ALU|BPF_LSH|BPF_X:
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case BPF_ALU|BPF_RSH|BPF_K:
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case BPF_ALU|BPF_RSH|BPF_X:
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case BPF_ALU|BPF_NEG:
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case BPF_LD|BPF_W|BPF_ABS:
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case BPF_LD|BPF_H|BPF_ABS:
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case BPF_LD|BPF_B|BPF_ABS:
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case BPF_LD|BPF_W|BPF_LEN:
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case BPF_LD|BPF_W|BPF_IND:
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case BPF_LD|BPF_H|BPF_IND:
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case BPF_LD|BPF_B|BPF_IND:
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case BPF_LD|BPF_IMM:
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case BPF_LDX|BPF_W|BPF_LEN:
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case BPF_LDX|BPF_B|BPF_MSH:
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case BPF_LDX|BPF_IMM:
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case BPF_MISC|BPF_TAX:
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case BPF_MISC|BPF_TXA:
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case BPF_RET|BPF_K:
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case BPF_RET|BPF_A:
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break;
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/* Some instructions need special checks */
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case BPF_ALU|BPF_DIV|BPF_K:
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/* check for division by zero */
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if (ftest->k == 0)
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return -EINVAL;
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break;
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case BPF_LD|BPF_MEM:
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case BPF_LDX|BPF_MEM:
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case BPF_ST:
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case BPF_STX:
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/* check for invalid memory addresses */
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if (ftest->k >= BPF_MEMWORDS)
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return -EINVAL;
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break;
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case BPF_JMP|BPF_JA:
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/*
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* Note, the large ftest->k might cause loops.
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* Compare this with conditional jumps below,
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* where offsets are limited. --ANK (981016)
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*/
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if (ftest->k >= (unsigned)(flen-pc-1))
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return -EINVAL;
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break;
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case BPF_JMP|BPF_JEQ|BPF_K:
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case BPF_JMP|BPF_JEQ|BPF_X:
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case BPF_JMP|BPF_JGE|BPF_K:
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case BPF_JMP|BPF_JGE|BPF_X:
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case BPF_JMP|BPF_JGT|BPF_K:
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case BPF_JMP|BPF_JGT|BPF_X:
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case BPF_JMP|BPF_JSET|BPF_K:
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case BPF_JMP|BPF_JSET|BPF_X:
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/* for conditionals both must be safe */
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if (pc + ftest->jt + 1 >= flen ||
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pc + ftest->jf + 1 >= flen)
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return -EINVAL;
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break;
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default:
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return -EINVAL;
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}
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}
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return (BPF_CLASS(filter[flen - 1].code) == BPF_RET) ? 0 : -EINVAL;
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}
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EXPORT_SYMBOL(sk_chk_filter);
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/**
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* sk_filter_rcu_release: Release a socket filter by rcu_head
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* @rcu: rcu_head that contains the sk_filter to free
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*/
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static void sk_filter_rcu_release(struct rcu_head *rcu)
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{
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struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);
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sk_filter_release(fp);
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}
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static void sk_filter_delayed_uncharge(struct sock *sk, struct sk_filter *fp)
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{
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unsigned int size = sk_filter_len(fp);
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atomic_sub(size, &sk->sk_omem_alloc);
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call_rcu_bh(&fp->rcu, sk_filter_rcu_release);
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}
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/**
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* sk_attach_filter - attach a socket filter
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* @fprog: the filter program
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* @sk: the socket to use
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*
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* Attach the user's filter code. We first run some sanity checks on
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* it to make sure it does not explode on us later. If an error
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* occurs or there is insufficient memory for the filter a negative
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* errno code is returned. On success the return is zero.
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*/
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int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
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{
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struct sk_filter *fp, *old_fp;
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unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
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int err;
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/* Make sure new filter is there and in the right amounts. */
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if (fprog->filter == NULL)
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return -EINVAL;
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fp = sock_kmalloc(sk, fsize+sizeof(*fp), GFP_KERNEL);
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if (!fp)
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return -ENOMEM;
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if (copy_from_user(fp->insns, fprog->filter, fsize)) {
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sock_kfree_s(sk, fp, fsize+sizeof(*fp));
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return -EFAULT;
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}
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atomic_set(&fp->refcnt, 1);
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fp->len = fprog->len;
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err = sk_chk_filter(fp->insns, fp->len);
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if (err) {
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sk_filter_uncharge(sk, fp);
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return err;
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}
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rcu_read_lock_bh();
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old_fp = rcu_dereference(sk->sk_filter);
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rcu_assign_pointer(sk->sk_filter, fp);
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rcu_read_unlock_bh();
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if (old_fp)
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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;
|
|
}
|