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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /net/core/filter.c
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'net/core/filter.c')
-rw-r--r--net/core/filter.c432
1 files changed, 432 insertions, 0 deletions
diff --git a/net/core/filter.c b/net/core/filter.c
new file mode 100644
index 00000000000..f3b88205ace
--- /dev/null
+++ b/net/core/filter.c
@@ -0,0 +1,432 @@
+/*
+ * 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.
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/sched.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 <linux/filter.h>
+
+/* No hurry in this branch */
+static u8 *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;
+}
+
+/**
+ * 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.
+ */
+
+int sk_run_filter(struct sk_buff *skb, struct sock_filter *filter, int flen)
+{
+ unsigned char *data = skb->data;
+ /* len is UNSIGNED. Byte wide insns relies only on implicit
+ type casts to prevent reading arbitrary memory locations.
+ */
+ unsigned int len = skb->len-skb->data_len;
+ struct sock_filter *fentry; /* We walk down these */
+ u32 A = 0; /* Accumulator */
+ u32 X = 0; /* Index Register */
+ u32 mem[BPF_MEMWORDS]; /* Scratch Memory Store */
+ 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:
+ if (fentry->k == 0)
+ return 0;
+ 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:
+ if (k >= 0 && (unsigned int)(k+sizeof(u32)) <= len) {
+ A = ntohl(*(u32*)&data[k]);
+ continue;
+ }
+ if (k < 0) {
+ u8 *ptr;
+
+ if (k >= SKF_AD_OFF)
+ break;
+ ptr = load_pointer(skb, k);
+ if (ptr) {
+ A = ntohl(*(u32*)ptr);
+ continue;
+ }
+ } else {
+ u32 _tmp, *p;
+ p = skb_header_pointer(skb, k, 4, &_tmp);
+ if (p != NULL) {
+ A = ntohl(*p);
+ continue;
+ }
+ }
+ return 0;
+ case BPF_LD|BPF_H|BPF_ABS:
+ k = fentry->k;
+ load_h:
+ if (k >= 0 && (unsigned int)(k + sizeof(u16)) <= len) {
+ A = ntohs(*(u16*)&data[k]);
+ continue;
+ }
+ if (k < 0) {
+ u8 *ptr;
+
+ if (k >= SKF_AD_OFF)
+ break;
+ ptr = load_pointer(skb, k);
+ if (ptr) {
+ A = ntohs(*(u16*)ptr);
+ continue;
+ }
+ } else {
+ u16 _tmp, *p;
+ p = skb_header_pointer(skb, k, 2, &_tmp);
+ if (p != NULL) {
+ A = ntohs(*p);
+ continue;
+ }
+ }
+ return 0;
+ case BPF_LD|BPF_B|BPF_ABS:
+ k = fentry->k;
+load_b:
+ if (k >= 0 && (unsigned int)k < len) {
+ A = data[k];
+ continue;
+ }
+ if (k < 0) {
+ u8 *ptr;
+
+ if (k >= SKF_AD_OFF)
+ break;
+ ptr = load_pointer(skb, k);
+ if (ptr) {
+ A = *ptr;
+ continue;
+ }
+ } else {
+ u8 _tmp, *p;
+ p = skb_header_pointer(skb, k, 1, &_tmp);
+ if (p != NULL) {
+ A = *p;
+ continue;
+ }
+ }
+ return 0;
+ case BPF_LD|BPF_W|BPF_LEN:
+ A = len;
+ continue;
+ case BPF_LDX|BPF_W|BPF_LEN:
+ X = 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:
+ if (fentry->k >= len)
+ return 0;
+ X = (data[fentry->k] & 0xf) << 2;
+ continue;
+ 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 ((unsigned int)fentry->k);
+ case BPF_RET|BPF_A:
+ return ((unsigned int)A);
+ case BPF_ST:
+ mem[fentry->k] = A;
+ continue;
+ case BPF_STX:
+ mem[fentry->k] = X;
+ continue;
+ default:
+ /* Invalid instruction counts as RET */
+ 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 = htons(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 no backward jumps. It must end with a RET instruction
+ *
+ * Returns 0 if the rule set is legal or a negative errno code if not.
+ */
+int sk_chk_filter(struct sock_filter *filter, int flen)
+{
+ struct sock_filter *ftest;
+ int pc;
+
+ if (((unsigned int)flen >= (~0U / sizeof(struct sock_filter))) || flen == 0)
+ return -EINVAL;
+
+ /* check the filter code now */
+ for (pc = 0; pc < flen; pc++) {
+ /* all jumps are forward as they are not signed */
+ ftest = &filter[pc];
+ if (BPF_CLASS(ftest->code) == BPF_JMP) {
+ /* but they mustn't jump off the end */
+ if (BPF_OP(ftest->code) == 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;
+ } else {
+ /* for conditionals both must be safe */
+ if (pc + ftest->jt +1 >= flen ||
+ pc + ftest->jf +1 >= flen)
+ return -EINVAL;
+ }
+ }
+
+ /* check that memory operations use valid addresses. */
+ if (ftest->k >= BPF_MEMWORDS) {
+ /* but it might not be a memory operation... */
+ switch (ftest->code) {
+ case BPF_ST:
+ case BPF_STX:
+ case BPF_LD|BPF_MEM:
+ case BPF_LDX|BPF_MEM:
+ return -EINVAL;
+ }
+ }
+ }
+
+ /*
+ * The program must end with a return. We don't care where they
+ * jumped within the script (its always forwards) but in the end
+ * they _will_ hit this.
+ */
+ 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 || fprog->len > BPF_MAXINSNS)
+ 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;
+
+ spin_lock_bh(&sk->sk_lock.slock);
+ old_fp = sk->sk_filter;
+ sk->sk_filter = fp;
+ spin_unlock_bh(&sk->sk_lock.slock);
+ fp = old_fp;
+ }
+
+ if (fp)
+ sk_filter_release(sk, fp);
+ return err;
+}
+
+EXPORT_SYMBOL(sk_chk_filter);
+EXPORT_SYMBOL(sk_run_filter);