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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 <net/ip.h>
- #include <net/protocol.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->nh.raw + k - SKF_NET_OFF;
- else if (k >= SKF_LL_OFF)
- ptr = skb->mac.raw + k - SKF_LL_OFF;
- if (ptr >= skb->head && ptr < skb->tail)
- 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_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 = ntohl(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 = ntohs(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;
- default:
- return 0;
- }
- }
- return 0;
- }
- /**
- * 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;
- }
- /**
- * 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;
- 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) {
- struct sk_filter *old_fp;
- rcu_read_lock_bh();
- old_fp = rcu_dereference(sk->sk_filter);
- rcu_assign_pointer(sk->sk_filter, fp);
- rcu_read_unlock_bh();
- fp = old_fp;
- }
- if (fp)
- sk_filter_release(sk, fp);
- return err;
- }
- EXPORT_SYMBOL(sk_chk_filter);
- EXPORT_SYMBOL(sk_run_filter);
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