- 根目录:
- net
- core
- filter.c
/*
* Linux Socket Filter - Kernel level socket filtering
*
* Based on the design of the Berkeley Packet Filter. The new
* internal format has been designed by PLUMgrid:
*
* Copyright (c) 2011 - 2014 PLUMgrid, http://plumgrid.com
*
* Authors:
*
* Jay Schulist <jschlst@samba.org>
* Alexei Starovoitov <ast@plumgrid.com>
* Daniel Borkmann <dborkman@redhat.com>
*
* 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 bpf_check_classic()
*/
#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/ratelimit.h>
#include <linux/seccomp.h>
#include <linux/if_vlan.h>
/**
* 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;
/*
* If the skb was allocated from pfmemalloc reserves, only
* allow SOCK_MEMALLOC sockets to use it as this socket is
* helping free memory
*/
if (skb_pfmemalloc(skb) && !sock_flag(sk, SOCK_MEMALLOC))
return -ENOMEM;
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);
static u64 __skb_get_pay_offset(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
{
return skb_get_poff((struct sk_buff *)(unsigned long) ctx);
}
static u64 __skb_get_nlattr(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
{
struct sk_buff *skb = (struct sk_buff *)(unsigned long) ctx;
struct nlattr *nla;
if (skb_is_nonlinear(skb))
return 0;
if (skb->len < sizeof(struct nlattr))
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)
return (void *) nla - (void *) skb->data;
return 0;
}
static u64 __skb_get_nlattr_nest(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
{
struct sk_buff *skb = (struct sk_buff *)(unsigned long) ctx;
struct nlattr *nla;
if (skb_is_nonlinear(skb))
return 0;
if (skb->len < sizeof(struct nlattr))
return 0;
if (a > skb->len - sizeof(struct nlattr))
return 0;
nla = (struct nlattr *) &skb->data[a];
if (nla->nla_len > skb->len - a)
return 0;
nla = nla_find_nested(nla, x);
if (nla)
return (void *) nla - (void *) skb->data;
return 0;
}
static u64 __get_raw_cpu_id(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
{
return raw_smp_processor_id();
}
/* note that this only generates 32-bit random numbers */
static u64 __get_random_u32(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
{
return prandom_u32();
}
static bool convert_bpf_extensions(struct sock_filter *fp,
struct bpf_insn **insnp)
{
struct bpf_insn *insn = *insnp;
switch (fp->k) {
case SKF_AD_OFF + SKF_AD_PROTOCOL:
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);
/* A = *(u16 *) (CTX + offsetof(protocol)) */
*insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
offsetof(struct sk_buff, protocol));
/* A = ntohs(A) [emitting a nop or swap16] */
*insn = BPF_ENDIAN(BPF_FROM_BE, BPF_REG_A, 16);
break;
case SKF_AD_OFF + SKF_AD_PKTTYPE:
*insn++ = BPF_LDX_MEM(BPF_B, BPF_REG_A, BPF_REG_CTX,
PKT_TYPE_OFFSET());
*insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, PKT_TYPE_MAX);
#ifdef __BIG_ENDIAN_BITFIELD
insn++;
*insn = BPF_ALU32_IMM(BPF_RSH, BPF_REG_A, 5);
#endif
break;
case SKF_AD_OFF + SKF_AD_IFINDEX:
case SKF_AD_OFF + SKF_AD_HATYPE:
BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);
BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, type) != 2);
BUILD_BUG_ON(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, dev)) < 0);
*insn++ = BPF_LDX_MEM(bytes_to_bpf_size(FIELD_SIZEOF(struct sk_buff, dev)),
BPF_REG_TMP, BPF_REG_CTX,
offsetof(struct sk_buff, dev));
/* if (tmp != 0) goto pc + 1 */
*insn++ = BPF_JMP_IMM(BPF_JNE, BPF_REG_TMP, 0, 1);
*insn++ = BPF_EXIT_INSN();
if (fp->k == SKF_AD_OFF + SKF_AD_IFINDEX)
*insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_TMP,
offsetof(struct net_device, ifindex));
else
*insn = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_TMP,
offsetof(struct net_device, type));
break;
case SKF_AD_OFF + SKF_AD_MARK:
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
*insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_CTX,
offsetof(struct sk_buff, mark));
break;
case SKF_AD_OFF + SKF_AD_RXHASH:
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);
*insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_CTX,
offsetof(struct sk_buff, hash));
break;
case SKF_AD_OFF + SKF_AD_QUEUE:
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, queue_mapping) != 2);
*insn = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
offsetof(struct sk_buff, queue_mapping));
break;
case SKF_AD_OFF + SKF_AD_VLAN_TAG:
case SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT:
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);
BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);
/* A = *(u16 *) (CTX + offsetof(vlan_tci)) */
*insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,
offsetof(struct sk_buff, vlan_tci));
if (fp->k == SKF_AD_OFF + SKF_AD_VLAN_TAG) {
*insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A,
~VLAN_TAG_PRESENT);
} else {
/* A >>= 12 */
*insn++ = BPF_ALU32_IMM(BPF_RSH, BPF_REG_A, 12);
/* A &= 1 */
*insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, 1);
}
break;
case SKF_AD_OFF + SKF_AD_PAY_OFFSET:
case SKF_AD_OFF + SKF_AD_NLATTR:
case SKF_AD_OFF + SKF_AD_NLATTR_NEST:
case SKF_AD_OFF + SKF_AD_CPU:
case SKF_AD_OFF + SKF_AD_RANDOM:
/* arg1 = CTX */
*insn++ = BPF_MOV64_REG(BPF_REG_ARG1, BPF_REG_CTX);
/* arg2 = A */
*insn++ = BPF_MOV64_REG(BPF_REG_ARG2, BPF_REG_A);
/* arg3 = X */
*insn++ = BPF_MOV64_REG(BPF_REG_ARG3, BPF_REG_X);
/* Emit call(arg1=CTX, arg2=A, arg3=X) */
switch (fp->k) {
case SKF_AD_OFF + SKF_AD_PAY_OFFSET:
*insn = BPF_EMIT_CALL(__skb_get_pay_offset);
break;
case SKF_AD_OFF + SKF_AD_NLATTR:
*insn = BPF_EMIT_CALL(__skb_get_nlattr);
break;
case SKF_AD_OFF + SKF_AD_NLATTR_NEST:
*insn = BPF_EMIT_CALL(__skb_get_nlattr_nest);
break;
case SKF_AD_OFF + SKF_AD_CPU:
*insn = BPF_EMIT_CALL(__get_raw_cpu_id);
break;
case SKF_AD_OFF + SKF_AD_RANDOM:
*insn = BPF_EMIT_CALL(__get_random_u32);
break;
}
break;
case SKF_AD_OFF + SKF_AD_ALU_XOR_X:
/* A ^= X */
*insn = BPF_ALU32_REG(BPF_XOR, BPF_REG_A, BPF_REG_X);
break;
default:
/* This is just a dummy call to avoid letting the compiler
* evict __bpf_call_base() as an optimization. Placed here
* where no-one bothers.
*/
BUG_ON(__bpf_call_base(0, 0, 0, 0, 0) != 0);
return false;
}
*insnp = insn;
return true;
}
/**
* bpf_convert_filter - convert filter program
* @prog: the user passed filter program
* @len: the length of the user passed filter program
* @new_prog: buffer where converted program will be stored
* @new_len: pointer to store length of converted program
*
* Remap 'sock_filter' style BPF instruction set to 'sock_filter_ext' style.
* Conversion workflow:
*
* 1) First pass for calculating the new program length:
* bpf_convert_filter(old_prog, old_len, NULL, &new_len)
*
* 2) 2nd pass to remap in two passes: 1st pass finds new
* jump offsets, 2nd pass remapping:
* new_prog = kmalloc(sizeof(struct bpf_insn) * new_len);
* bpf_convert_filter(old_prog, old_len, new_prog, &new_len);
*
* User BPF's register A is mapped to our BPF register 6, user BPF
* register X is mapped to BPF register 7; frame pointer is always
* register 10; Context 'void *ctx' is stored in register 1, that is,
* for socket filters: ctx == 'struct sk_buff *', for seccomp:
* ctx == 'struct seccomp_data *'.
*/
int bpf_convert_filter(struct sock_filter *prog, int len,
struct bpf_insn *new_prog, int *new_len)
{
int new_flen = 0, pass = 0, target, i;
struct bpf_insn *new_insn;
struct sock_filter *fp;
int *addrs = NULL;
u8 bpf_src;
BUILD_BUG_ON(BPF_MEMWORDS * sizeof(u32) > MAX_BPF_STACK);
BUILD_BUG_ON(BPF_REG_FP + 1 != MAX_BPF_REG);
if (len <= 0 || len > BPF_MAXINSNS)
return -EINVAL;
if (new_prog) {
addrs = kcalloc(len, sizeof(*addrs), GFP_KERNEL);
if (!addrs)
return -ENOMEM;
}
do_pass:
new_insn = new_prog;
fp = prog;
if (new_insn)
*new_insn = BPF_MOV64_REG(BPF_REG_CTX, BPF_REG_ARG1);
new_insn++;
for (i = 0; i < len; fp++, i++) {
struct bpf_insn tmp_insns[6] = { };
struct bpf_insn *insn = tmp_insns;
if (addrs)
addrs[i] = new_insn - new_prog;
switch (fp->code) {
/* All arithmetic insns and skb loads map as-is. */
case BPF_ALU | BPF_ADD | BPF_X:
case BPF_ALU | BPF_ADD | BPF_K:
case BPF_ALU | BPF_SUB | BPF_X:
case BPF_ALU | BPF_SUB | BPF_K:
case BPF_ALU | BPF_AND | BPF_X:
case BPF_ALU | BPF_AND | BPF_K:
case BPF_ALU | BPF_OR | BPF_X:
case BPF_ALU | BPF_OR | BPF_K:
case BPF_ALU | BPF_LSH | BPF_X:
case BPF_ALU | BPF_LSH | BPF_K:
case BPF_ALU | BPF_RSH | BPF_X:
case BPF_ALU | BPF_RSH | BPF_K:
case BPF_ALU | BPF_XOR | BPF_X:
case BPF_ALU | BPF_XOR | BPF_K:
case BPF_ALU | BPF_MUL | BPF_X:
case BPF_ALU | BPF_MUL | BPF_K:
case BPF_ALU | BPF_DIV | BPF_X:
case BPF_ALU | BPF_DIV | BPF_K:
case BPF_ALU | BPF_MOD | BPF_X:
case BPF_ALU | BPF_MOD | BPF_K:
case BPF_ALU | BPF_NEG:
case BPF_LD | BPF_ABS | BPF_W:
case BPF_LD | BPF_ABS | BPF_H:
case BPF_LD | BPF_ABS | BPF_B:
case BPF_LD | BPF_IND | BPF_W:
case BPF_LD | BPF_IND | BPF_H:
case BPF_LD | BPF_IND | BPF_B:
/* Check for overloaded BPF extension and
* directly convert it if found, otherwise
* just move on with mapping.
*/
if (BPF_CLASS(fp->code) == BPF_LD &&
BPF_MODE(fp->code) == BPF_ABS &&
convert_bpf_extensions(fp, &insn))
break;
*insn = BPF_RAW_INSN(fp->code, BPF_REG_A, BPF_REG_X, 0, fp->k);
break;
/* Jump transformation cannot use BPF block macros
* everywhere as offset calculation and target updates
* require a bit more work than the rest, i.e. jump
* opcodes map as-is, but offsets need adjustment.
*/
#define BPF_EMIT_JMP \
do { \
if (target >= len || target < 0) \
goto err; \
insn->off = addrs ? addrs[target] - addrs[i] - 1 : 0; \
/* Adjust pc relative offset for 2nd or 3rd insn. */ \
insn->off -= insn - tmp_insns; \
} while (0)
case BPF_JMP | BPF_JA:
target = i + fp->k + 1;
insn->code = fp->code;
BPF_EMIT_JMP;
break;
case BPF_JMP | BPF_JEQ | BPF_K:
case BPF_JMP | BPF_JEQ | BPF_X:
case BPF_JMP | BPF_JSET | BPF_K:
case BPF_JMP | BPF_JSET | BPF_X:
case BPF_JMP | BPF_JGT | BPF_K:
case BPF_JMP | BPF_JGT | BPF_X:
case BPF_JMP | BPF_JGE | BPF_K:
case BPF_JMP | BPF_JGE | BPF_X:
if (BPF_SRC(fp->code) == BPF_K && (int) fp->k < 0) {
/* BPF immediates are signed, zero extend
* immediate into tmp register and use it
* in compare insn.
*/
*insn++ = BPF_MOV32_IMM(BPF_REG_TMP, fp->k);
insn->dst_reg = BPF_REG_A;
insn->src_reg = BPF_REG_TMP;
bpf_src = BPF_X;
} else {
insn->dst_reg = BPF_REG_A;
insn->src_reg = BPF_REG_X;
insn->imm = fp->k;
bpf_src = BPF_SRC(fp->code);
}
/* Common case where 'jump_false' is next insn. */
if (fp->jf == 0) {
insn->code = BPF_JMP | BPF_OP(fp->code) | bpf_src;
target = i + fp->jt + 1;
BPF_EMIT_JMP;
break;
}
/* Convert JEQ into JNE when 'jump_true' is next insn. */
if (fp->jt == 0 && BPF_OP(fp->code) == BPF_JEQ) {
insn->code = BPF_JMP | BPF_JNE | bpf_src;
target = i + fp->jf + 1;
BPF_EMIT_JMP;
break;
}
/* Other jumps are mapped into two insns: Jxx and JA. */
target = i + fp->jt + 1;
insn->code = BPF_JMP | BPF_OP(fp->code) | bpf_src;
BPF_EMIT_JMP;
insn++;
insn->code = BPF_JMP | BPF_JA;
target = i + fp->jf + 1;
BPF_EMIT_JMP;
break;
/* ldxb 4 * ([14] & 0xf) is remaped into 6 insns. */
case BPF_LDX | BPF_MSH | BPF_B:
/* tmp = A */
*insn++ = BPF_MOV64_REG(BPF_REG_TMP, BPF_REG_A);
/* A = BPF_R0 = *(u8 *) (skb->data + K) */
*insn++ = BPF_LD_ABS(BPF_B, fp->k);
/* A &= 0xf */
*insn++ = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, 0xf);
/* A <<= 2 */
*insn++ = BPF_ALU32_IMM(BPF_LSH, BPF_REG_A, 2);
/* X = A */
*insn++ = BPF_MOV64_REG(BPF_REG_X, BPF_REG_A);
/* A = tmp */
*insn = BPF_MOV64_REG(BPF_REG_A, BPF_REG_TMP);
break;
/* RET_K, RET_A are remaped into 2 insns. */
case BPF_RET | BPF_A:
case BPF_RET | BPF_K:
*insn++ = BPF_MOV32_RAW(BPF_RVAL(fp->code) == BPF_K ?
BPF_K : BPF_X, BPF_REG_0,
BPF_REG_A, fp->k);
*insn = BPF_EXIT_INSN();
break;
/* Store to stack. */
case BPF_ST:
case BPF_STX:
*insn = BPF_STX_MEM(BPF_W, BPF_REG_FP, BPF_CLASS(fp->code) ==
BPF_ST ? BPF_REG_A : BPF_REG_X,
-(BPF_MEMWORDS - fp->k) * 4);
break;
/* Load from stack. */
case BPF_LD | BPF_MEM:
case BPF_LDX | BPF_MEM:
*insn = BPF_LDX_MEM(BPF_W, BPF_CLASS(fp->code) == BPF_LD ?
BPF_REG_A : BPF_REG_X, BPF_REG_FP,
-(BPF_MEMWORDS - fp->k) * 4);
break;
/* A = K or X = K */
case BPF_LD | BPF_IMM:
case BPF_LDX | BPF_IMM:
*insn = BPF_MOV32_IMM(BPF_CLASS(fp->code) == BPF_LD ?
BPF_REG_A : BPF_REG_X, fp->k);
break;
/* X = A */
case BPF_MISC | BPF_TAX:
*insn = BPF_MOV64_REG(BPF_REG_X, BPF_REG_A);
break;
/* A = X */
case BPF_MISC | BPF_TXA:
*insn = BPF_MOV64_REG(BPF_REG_A, BPF_REG_X);
break;
/* A = skb->len or X = skb->len */
case BPF_LD | BPF_W | BPF_LEN:
case BPF_LDX | BPF_W | BPF_LEN:
*insn = BPF_LDX_MEM(BPF_W, BPF_CLASS(fp->code) == BPF_LD ?
BPF_REG_A : BPF_REG_X, BPF_REG_CTX,
offsetof(struct sk_buff, len));
break;
/* Access seccomp_data fields. */
case BPF_LDX | BPF_ABS | BPF_W:
/* A = *(u32 *) (ctx + K) */
*insn = BPF_LDX_MEM(BPF_W, BPF_REG_A, BPF_REG_CTX, fp->k);
break;
/* Unkown instruction. */
default:
goto err;
}
insn++;
if (new_prog)
memcpy(new_insn, tmp_insns,
sizeof(*insn) * (insn - tmp_insns));
new_insn += insn - tmp_insns;
}
if (!new_prog) {
/* Only calculating new length. */
*new_len = new_insn - new_prog;
return 0;
}
pass++;
if (new_flen != new_insn - new_prog) {
new_flen = new_insn - new_prog;
if (pass > 2)
goto err;
goto do_pass;
}
kfree(addrs);
BUG_ON(*new_len != new_flen);
return 0;
err:
kfree(addrs);
return -EINVAL;
}
/* Security:
*
* As we dont want to clear mem[] array for each packet going through
* __bpf_prog_run(), we check that filter loaded by user never try to read
* a cell if not previously written, and we check all branches to be sure
* a malicious user doesn't try to abuse us.
*/
static int check_load_and_stores(const struct sock_filter *filter, int flen)
{
u16 *masks, memvalid = 0; /* One bit per cell, 16 cells */
int pc, ret = 0;
BUILD_BUG_ON(BPF_MEMWORDS > 16);
masks = kmalloc_array(flen, sizeof(*masks), GFP_KERNEL);
if (!masks)
return -ENOMEM;
memset(masks, 0xff, flen * sizeof(*masks));
for (pc = 0; pc < flen; pc++) {
memvalid &= masks[pc];
switch (filter[pc].code) {
case BPF_ST:
case BPF_STX:
memvalid |= (1 << filter[pc].k);
break;
case BPF_LD | BPF_MEM:
case BPF_LDX | BPF_MEM:
if (!(memvalid & (1 << filter[pc].k))) {
ret = -EINVAL;
goto error;
}
break;
case BPF_JMP | BPF_JA:
/* A jump must set masks on target */
masks[pc + 1 + filter[pc].k] &= memvalid;
memvalid = ~0;
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:
/* A jump must set masks on targets */
masks[pc + 1 + filter[pc].jt] &= memvalid;
masks[pc + 1 + filter[pc].jf] &= memvalid;
memvalid = ~0;
break;
}
}
error:
kfree(masks);
return ret;
}
static bool chk_code_allowed(u16 code_to_probe)
{
static const bool codes[] = {
/* 32 bit ALU operations */
[BPF_ALU | BPF_ADD | BPF_K] = true,
[BPF_ALU | BPF_ADD | BPF_X] = true,
[BPF_ALU | BPF_SUB | BPF_K] = true,
[BPF_ALU | BPF_SUB | BPF_X] = true,
[BPF_ALU | BPF_MUL | BPF_K] = true,
[BPF_ALU | BPF_MUL | BPF_X] = true,
[BPF_ALU | BPF_DIV | BPF_K] = true,
[BPF_ALU | BPF_DIV | BPF_X] = true,
[BPF_ALU | BPF_MOD | BPF_K] = true,
[BPF_ALU | BPF_MOD | BPF_X] = true,
[BPF_ALU | BPF_AND | BPF_K] = true,
[BPF_ALU | BPF_AND | BPF_X] = true,
[BPF_ALU | BPF_OR | BPF_K] = true,
[BPF_ALU | BPF_OR | BPF_X] = true,
[BPF_ALU | BPF_XOR | BPF_K] = true,
[BPF_ALU | BPF_XOR | BPF_X] = true,
[BPF_ALU | BPF_LSH | BPF_K] = true,
[BPF_ALU | BPF_LSH | BPF_X] = true,
[BPF_ALU | BPF_RSH | BPF_K] = true,
[BPF_ALU | BPF_RSH | BPF_X] = true,
[BPF_ALU | BPF_NEG] = true,
/* Load instructions */
[BPF_LD | BPF_W | BPF_ABS] = true,
[BPF_LD | BPF_H | BPF_ABS] = true,
[BPF_LD | BPF_B | BPF_ABS] = true,
[BPF_LD | BPF_W | BPF_LEN] = true,
[BPF_LD | BPF_W | BPF_IND] = true,
[BPF_LD | BPF_H | BPF_IND] = true,
[BPF_LD | BPF_B | BPF_IND] = true,
[BPF_LD | BPF_IMM] = true,
[BPF_LD | BPF_MEM] = true,
[BPF_LDX | BPF_W | BPF_LEN] = true,
[BPF_LDX | BPF_B | BPF_MSH] = true,
[BPF_LDX | BPF_IMM] = true,
[BPF_LDX | BPF_MEM] = true,
/* Store instructions */
[BPF_ST] = true,
[BPF_STX] = true,
/* Misc instructions */
[BPF_MISC | BPF_TAX] = true,
[BPF_MISC | BPF_TXA] = true,
/* Return instructions */
[BPF_RET | BPF_K] = true,
[BPF_RET | BPF_A] = true,
/* Jump instructions */
[BPF_JMP | BPF_JA] = true,
[BPF_JMP | BPF_JEQ | BPF_K] = true,
[BPF_JMP | BPF_JEQ | BPF_X] = true,
[BPF_JMP | BPF_JGE | BPF_K] = true,
[BPF_JMP | BPF_JGE | BPF_X] = true,
[BPF_JMP | BPF_JGT | BPF_K] = true,
[BPF_JMP | BPF_JGT | BPF_X] = true,
[BPF_JMP | BPF_JSET | BPF_K] = true,
[BPF_JMP | BPF_JSET | BPF_X] = true,
};
if (code_to_probe >= ARRAY_SIZE(codes))
return false;
return codes[code_to_probe];
}
/**
* bpf_check_classic - 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 bpf_check_classic(const struct sock_filter *filter, unsigned int flen)
{
bool anc_found;
int pc;
if (flen == 0 || flen > BPF_MAXINSNS)
return -EINVAL;
/* Check the filter code now */
for (pc = 0; pc < flen; pc++) {
const struct sock_filter *ftest = &filter[pc];
/* May we actually operate on this code? */
if (!chk_code_allowed(ftest->code))
return -EINVAL;
/* Some instructions need special checks */
switch (ftest->code) {
case BPF_ALU | BPF_DIV | BPF_K:
case BPF_ALU | BPF_MOD | 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 int)(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:
/* Both conditionals must be safe */
if (pc + ftest->jt + 1 >= flen ||
pc + ftest->jf + 1 >= flen)
return -EINVAL;
break;
case BPF_LD | BPF_W | BPF_ABS:
case BPF_LD | BPF_H | BPF_ABS:
case BPF_LD | BPF_B | BPF_ABS:
anc_found = false;
if (bpf_anc_helper(ftest) & BPF_ANC)
anc_found = true;
/* Ancillary operation unknown or unsupported */
if (anc_found == false && ftest->k >= SKF_AD_OFF)
return -EINVAL;
}
}
/* Last instruction must be a RET code */
switch (filter[flen - 1].code) {
case BPF_RET | BPF_K:
case BPF_RET | BPF_A:
return check_load_and_stores(filter, flen);
}
return -EINVAL;
}
EXPORT_SYMBOL(bpf_check_classic);
static int bpf_prog_store_orig_filter(struct bpf_prog *fp,
const struct sock_fprog *fprog)
{
unsigned int fsize = bpf_classic_proglen(fprog);
struct sock_fprog_kern *fkprog;
fp->orig_prog = kmalloc(sizeof(*fkprog), GFP_KERNEL);
if (!fp->orig_prog)
return -ENOMEM;
fkprog = fp->orig_prog;
fkprog->len = fprog->len;
fkprog->filter = kmemdup(fp->insns, fsize, GFP_KERNEL);
if (!fkprog->filter) {
kfree(fp->orig_prog);
return -ENOMEM;
}
return 0;
}
static void bpf_release_orig_filter(struct bpf_prog *fp)
{
struct sock_fprog_kern *fprog = fp->orig_prog;
if (fprog) {
kfree(fprog->filter);
kfree(fprog);
}
}
static void __bpf_prog_release(struct bpf_prog *prog)
{
bpf_release_orig_filter(prog);
bpf_prog_free(prog);
}
static void __sk_filter_release(struct sk_filter *fp)
{
__bpf_prog_release(fp->prog);
kfree(fp);
}
/**
* sk_filter_release_rcu - Release a socket filter by rcu_head
* @rcu: rcu_head that contains the sk_filter to free
*/
static void sk_filter_release_rcu(struct rcu_head *rcu)
{
struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu);
__sk_filter_release(fp);
}
/**
* sk_filter_release - release a socket filter
* @fp: filter to remove
*
* Remove a filter from a socket and release its resources.
*/
static void sk_filter_release(struct sk_filter *fp)
{
if (atomic_dec_and_test(&fp->refcnt))
call_rcu(&fp->rcu, sk_filter_release_rcu);
}
void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp)
{
u32 filter_size = bpf_prog_size(fp->prog->len);
atomic_sub(filter_size, &sk->sk_omem_alloc);
sk_filter_release(fp);
}
/* try to charge the socket memory if there is space available
* return true on success
*/
bool sk_filter_charge(struct sock *sk, struct sk_filter *fp)
{
u32 filter_size = bpf_prog_size(fp->prog->len);
/* same check as in sock_kmalloc() */
if (filter_size <= sysctl_optmem_max &&
atomic_read(&sk->sk_omem_alloc) + filter_size < sysctl_optmem_max) {
atomic_inc(&fp->refcnt);
atomic_add(filter_size, &sk->sk_omem_alloc);
return true;
}
return false;
}
static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp)
{
struct sock_filter *old_prog;
struct bpf_prog *old_fp;
int err, new_len, old_len = fp->len;
/* We are free to overwrite insns et al right here as it
* won't be used at this point in time anymore internally
* after the migration to the internal BPF instruction
* representation.
*/
BUILD_BUG_ON(sizeof(struct sock_filter) !=
sizeof(struct bpf_insn));
/* Conversion cannot happen on overlapping memory areas,
* so we need to keep the user BPF around until the 2nd
* pass. At this time, the user BPF is stored in fp->insns.
*/
old_prog = kmemdup(fp->insns, old_len * sizeof(struct sock_filter),
GFP_KERNEL);
if (!old_prog) {
err = -ENOMEM;
goto out_err;
}
/* 1st pass: calculate the new program length. */
err = bpf_convert_filter(old_prog, old_len, NULL, &new_len);
if (err)
goto out_err_free;
/* Expand fp for appending the new filter representation. */
old_fp = fp;
fp = bpf_prog_realloc(old_fp, bpf_prog_size(new_len), 0);
if (!fp) {
/* The old_fp is still around in case we couldn't
* allocate new memory, so uncharge on that one.
*/
fp = old_fp;
err = -ENOMEM;
goto out_err_free;
}
fp->len = new_len;
/* 2nd pass: remap sock_filter insns into bpf_insn insns. */
err = bpf_convert_filter(old_prog, old_len, fp->insnsi, &new_len);
if (err)
/* 2nd bpf_convert_filter() can fail only if it fails
* to allocate memory, remapping must succeed. Note,
* that at this time old_fp has already been released
* by krealloc().
*/
goto out_err_free;
bpf_prog_select_runtime(fp);
kfree(old_prog);
return fp;
out_err_free:
kfree(old_prog);
out_err:
__bpf_prog_release(fp);
return ERR_PTR(err);
}
static struct bpf_prog *bpf_prepare_filter(struct bpf_prog *fp)
{
int err;
fp->bpf_func = NULL;
fp->jited = false;
err = bpf_check_classic(fp->insns, fp->len);
if (err) {
__bpf_prog_release(fp);
return ERR_PTR(err);
}
/* Probe if we can JIT compile the filter and if so, do
* the compilation of the filter.
*/
bpf_jit_compile(fp);
/* JIT compiler couldn't process this filter, so do the
* internal BPF translation for the optimized interpreter.
*/
if (!fp->jited)
fp = bpf_migrate_filter(fp);
return fp;
}
/**
* bpf_prog_create - create an unattached filter
* @pfp: the unattached filter that is created
* @fprog: the filter program
*
* Create a filter independent of any socket. 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 bpf_prog_create(struct bpf_prog **pfp, struct sock_fprog_kern *fprog)
{
unsigned int fsize = bpf_classic_proglen(fprog);
struct bpf_prog *fp;
/* Make sure new filter is there and in the right amounts. */
if (fprog->filter == NULL)
return -EINVAL;
fp = bpf_prog_alloc(bpf_prog_size(fprog->len), 0);
if (!fp)
return -ENOMEM;
memcpy(fp->insns, fprog->filter, fsize);
fp->len = fprog->len;
/* Since unattached filters are not copied back to user
* space through sk_get_filter(), we do not need to hold
* a copy here, and can spare us the work.
*/
fp->orig_prog = NULL;
/* bpf_prepare_filter() already takes care of freeing
* memory in case something goes wrong.
*/
fp = bpf_prepare_filter(fp);
if (IS_ERR(fp))
return PTR_ERR(fp);
*pfp = fp;
return 0;
}
EXPORT_SYMBOL_GPL(bpf_prog_create);
void bpf_prog_destroy(struct bpf_prog *fp)
{
__bpf_prog_release(fp);
}
EXPORT_SYMBOL_GPL(bpf_prog_destroy);
/**
* 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 = bpf_classic_proglen(fprog);
unsigned int bpf_fsize = bpf_prog_size(fprog->len);
struct bpf_prog *prog;
int err;
if (sock_flag(sk, SOCK_FILTER_LOCKED))
return -EPERM;
/* Make sure new filter is there and in the right amounts. */
if (fprog->filter == NULL)
return -EINVAL;
prog = bpf_prog_alloc(bpf_fsize, 0);
if (!prog)
return -ENOMEM;
if (copy_from_user(prog->insns, fprog->filter, fsize)) {
__bpf_prog_free(prog);
return -EFAULT;
}
prog->len = fprog->len;
err = bpf_prog_store_orig_filter(prog, fprog);
if (err) {
__bpf_prog_free(prog);
return -ENOMEM;
}
/* bpf_prepare_filter() already takes care of freeing
* memory in case something goes wrong.
*/
prog = bpf_prepare_filter(prog);
if (IS_ERR(prog))
return PTR_ERR(prog);
fp = kmalloc(sizeof(*fp), GFP_KERNEL);
if (!fp) {
__bpf_prog_release(prog);
return -ENOMEM;
}
fp->prog = prog;
atomic_set(&fp->refcnt, 0);
if (!sk_filter_charge(sk, fp)) {
__sk_filter_release(fp);
return -ENOMEM;
}
old_fp = rcu_dereference_protected(sk->sk_filter,
sock_owned_by_user(sk));
rcu_assign_pointer(sk->sk_filter, fp);
if (old_fp)
sk_filter_uncharge(sk, old_fp);
return 0;
}
EXPORT_SYMBOL_GPL(sk_attach_filter);
int sk_detach_filter(struct sock *sk)
{
int ret = -ENOENT;
struct sk_filter *filter;
if (sock_flag(sk, SOCK_FILTER_LOCKED))
return -EPERM;
filter = rcu_dereference_protected(sk->sk_filter,
sock_owned_by_user(sk));
if (filter) {
RCU_INIT_POINTER(sk->sk_filter, NULL);
sk_filter_uncharge(sk, filter);
ret = 0;
}
return ret;
}
EXPORT_SYMBOL_GPL(sk_detach_filter);
int sk_get_filter(struct sock *sk, struct sock_filter __user *ubuf,
unsigned int len)
{
struct sock_fprog_kern *fprog;
struct sk_filter *filter;
int ret = 0;
lock_sock(sk);
filter = rcu_dereference_protected(sk->sk_filter,
sock_owned_by_user(sk));
if (!filter)
goto out;
/* We're copying the filter that has been originally attached,
* so no conversion/decode needed anymore.
*/
fprog = filter->prog->orig_prog;
ret = fprog->len;
if (!len)
/* User space only enquires number of filter blocks. */
goto out;
ret = -EINVAL;
if (len < fprog->len)
goto out;
ret = -EFAULT;
if (copy_to_user(ubuf, fprog->filter, bpf_classic_proglen(fprog)))
goto out;
/* Instead of bytes, the API requests to return the number
* of filter blocks.
*/
ret = fprog->len;
out:
release_sock(sk);
return ret;
}