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bpf: add unprivileged bpf tests 

Add new tests samples/bpf/test_verifier:

unpriv: return pointer
  checks that pointer cannot be returned from the eBPF program

unpriv: add const to pointer
unpriv: add pointer to pointer
unpriv: neg pointer
  checks that pointer arithmetic is disallowed

unpriv: cmp pointer with const
unpriv: cmp pointer with pointer
  checks that comparison of pointers is disallowed
  Only one case allowed 'void *value = bpf_map_lookup_elem(..); if (value == 0) ...'

unpriv: check that printk is disallowed
  since bpf_trace_printk is not available to unprivileged

unpriv: pass pointer to helper function
  checks that pointers cannot be passed to functions that expect integers
  If function expects a pointer the verifier allows only that type of pointer.
  Like 1st argument of bpf_map_lookup_elem() must be pointer to map.
  (applies to non-root as well)

unpriv: indirectly pass pointer on stack to helper function
  checks that pointer stored into stack cannot be used as part of key
  passed into bpf_map_lookup_elem()

unpriv: mangle pointer on stack 1
unpriv: mangle pointer on stack 2
  checks that writing into stack slot that already contains a pointer
  is disallowed

unpriv: read pointer from stack in small chunks
  checks that < 8 byte read from stack slot that contains a pointer is
  disallowed

unpriv: write pointer into ctx
  checks that storing pointers into skb->fields is disallowed

unpriv: write pointer into map elem value
  checks that storing pointers into element values is disallowed
  For example:
  int bpf_prog(struct __sk_buff *skb)
  {
    u32 key = 0;
    u64 *value = bpf_map_lookup_elem(&map, &key);
    if (value)
       *value = (u64) skb;
  }
  will be rejected.

unpriv: partial copy of pointer
  checks that doing 32-bit register mov from register containing
  a pointer is disallowed

unpriv: pass pointer to tail_call
  checks that passing pointer as an index into bpf_tail_call
  is disallowed

unpriv: cmp map pointer with zero
  checks that comparing map pointer with constant is disallowed

unpriv: write into frame pointer
  checks that frame pointer is read-only (applies to root too)

unpriv: cmp of frame pointer
  checks that R10 cannot be using in comparison

unpriv: cmp of stack pointer
  checks that Rx = R10 - imm is ok, but comparing Rx is not

unpriv: obfuscate stack pointer
  checks that Rx = R10 - imm is ok, but Rx -= imm is not

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov 2015-10-07 22:23:23 -07:00 committed by David S. Miller
parent aaac3ba95e
commit bf5088773f
2 changed files with 355 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
samples/bpf/libbpf.h
View File

@ -64,6 +64,14 @@ extern char bpf_log_buf[LOG_BUF_SIZE];
.off = 0, \
.imm = 0 })
#define BPF_MOV32_REG(DST, SRC) \
((struct bpf_insn) { \
.code = BPF_ALU | BPF_MOV | BPF_X, \
.dst_reg = DST, \
.src_reg = SRC, \
.off = 0, \
.imm = 0 })
/* Short form of mov, dst_reg = imm32 */
#define BPF_MOV64_IMM(DST, IMM) \

357
samples/bpf/test_verifier.c
View File

@ -15,20 +15,27 @@
#include <string.h>
#include <linux/filter.h>
#include <stddef.h>
#include <stdbool.h>
#include <sys/resource.h>
#include "libbpf.h"
#define MAX_INSNS 512
#define ARRAY_SIZE(x) (sizeof(x) / sizeof(*(x)))
#define MAX_FIXUPS 8
struct bpf_test {
const char *descr;
struct bpf_insn insns[MAX_INSNS];
int fixup[32];
int fixup[MAX_FIXUPS];
int prog_array_fixup[MAX_FIXUPS];
const char *errstr;
const char *errstr_unpriv;
enum {
UNDEF,
ACCEPT,
REJECT
} result;
} result, result_unpriv;
enum bpf_prog_type prog_type;
};
@ -96,6 +103,7 @@ static struct bpf_test tests[] = {
BPF_EXIT_INSN(),
},
.errstr = "invalid BPF_LD_IMM insn",
.errstr_unpriv = "R1 pointer comparison",
.result = REJECT,
},
{
@ -109,6 +117,7 @@ static struct bpf_test tests[] = {
BPF_EXIT_INSN(),
},
.errstr = "invalid BPF_LD_IMM insn",
.errstr_unpriv = "R1 pointer comparison",
.result = REJECT,
},
{
@ -219,6 +228,7 @@ static struct bpf_test tests[] = {
BPF_EXIT_INSN(),
},
.errstr = "R0 !read_ok",
.errstr_unpriv = "R1 pointer comparison",
.result = REJECT,
},
{
@ -294,7 +304,9 @@ static struct bpf_test tests[] = {
BPF_MOV64_REG(BPF_REG_0, BPF_REG_2),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "R0 leaks addr",
.result = ACCEPT,
.result_unpriv = REJECT,
},
{
"check corrupted spill/fill",
@ -310,6 +322,7 @@ static struct bpf_test tests[] = {
BPF_EXIT_INSN(),
},
.errstr_unpriv = "attempt to corrupt spilled",
.errstr = "corrupted spill",
.result = REJECT,
},
@ -473,6 +486,7 @@ static struct bpf_test tests[] = {
},
.fixup = {3},
.errstr = "R0 invalid mem access",
.errstr_unpriv = "R0 leaks addr",
.result = REJECT,
},
{
@ -495,6 +509,8 @@ static struct bpf_test tests[] = {
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "R1 pointer comparison",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
@ -521,6 +537,8 @@ static struct bpf_test tests[] = {
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "R1 pointer comparison",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
@ -555,6 +573,8 @@ static struct bpf_test tests[] = {
BPF_EXIT_INSN(),
},
.fixup = {24},
.errstr_unpriv = "R1 pointer comparison",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
@ -603,6 +623,8 @@ static struct bpf_test tests[] = {
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "R1 pointer comparison",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
@ -642,6 +664,8 @@ static struct bpf_test tests[] = {
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "R1 pointer comparison",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
@ -699,6 +723,7 @@ static struct bpf_test tests[] = {
},
.fixup = {4},
.errstr = "different pointers",
.errstr_unpriv = "R1 pointer comparison",
.result = REJECT,
},
{
@ -720,6 +745,7 @@ static struct bpf_test tests[] = {
},
.fixup = {6},
.errstr = "different pointers",
.errstr_unpriv = "R1 pointer comparison",
.result = REJECT,
},
{
@ -742,6 +768,7 @@ static struct bpf_test tests[] = {
},
.fixup = {7},
.errstr = "different pointers",
.errstr_unpriv = "R1 pointer comparison",
.result = REJECT,
},
{
@ -752,6 +779,7 @@ static struct bpf_test tests[] = {
BPF_EXIT_INSN(),
},
.errstr = "invalid bpf_context access",
.errstr_unpriv = "R1 leaks addr",
.result = REJECT,
},
{
@ -762,6 +790,7 @@ static struct bpf_test tests[] = {
BPF_EXIT_INSN(),
},
.errstr = "invalid bpf_context access",
.errstr_unpriv = "R1 leaks addr",
.result = REJECT,
},
{
@ -772,16 +801,18 @@ static struct bpf_test tests[] = {
BPF_EXIT_INSN(),
},
.errstr = "invalid bpf_context access",
.errstr_unpriv = "R1 leaks addr",
.result = REJECT,
},
{
"check out of range skb->cb access",
.insns = {
BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,
offsetof(struct __sk_buff, cb[60])),
offsetof(struct __sk_buff, cb[0]) + 256),
BPF_EXIT_INSN(),
},
.errstr = "invalid bpf_context access",
.errstr_unpriv = "",
.result = REJECT,
.prog_type = BPF_PROG_TYPE_SCHED_ACT,
},
@ -803,6 +834,8 @@ static struct bpf_test tests[] = {
BPF_EXIT_INSN(),
},
.result = ACCEPT,
.errstr_unpriv = "R1 leaks addr",
.result_unpriv = REJECT,
},
{
"write skb fields from tc_cls_act prog",
@ -819,6 +852,8 @@ static struct bpf_test tests[] = {
offsetof(struct __sk_buff, cb[3])),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "",
.result_unpriv = REJECT,
.result = ACCEPT,
.prog_type = BPF_PROG_TYPE_SCHED_CLS,
},
@ -881,6 +916,270 @@ static struct bpf_test tests[] = {
.result = REJECT,
.errstr = "invalid stack off=0 size=8",
},
{
"unpriv: return pointer",
.insns = {
BPF_MOV64_REG(BPF_REG_0, BPF_REG_10),
BPF_EXIT_INSN(),
},
.result = ACCEPT,
.result_unpriv = REJECT,
.errstr_unpriv = "R0 leaks addr",
},
{
"unpriv: add const to pointer",
.insns = {
BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, 8),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.result = ACCEPT,
.result_unpriv = REJECT,
.errstr_unpriv = "R1 pointer arithmetic",
},
{
"unpriv: add pointer to pointer",
.insns = {
BPF_ALU64_REG(BPF_ADD, BPF_REG_1, BPF_REG_10),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.result = ACCEPT,
.result_unpriv = REJECT,
.errstr_unpriv = "R1 pointer arithmetic",
},
{
"unpriv: neg pointer",
.insns = {
BPF_ALU64_IMM(BPF_NEG, BPF_REG_1, 0),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.result = ACCEPT,
.result_unpriv = REJECT,
.errstr_unpriv = "R1 pointer arithmetic",
},
{
"unpriv: cmp pointer with const",
.insns = {
BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0, 0),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.result = ACCEPT,
.result_unpriv = REJECT,
.errstr_unpriv = "R1 pointer comparison",
},
{
"unpriv: cmp pointer with pointer",
.insns = {
BPF_JMP_REG(BPF_JEQ, BPF_REG_1, BPF_REG_10, 0),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.result = ACCEPT,
.result_unpriv = REJECT,
.errstr_unpriv = "R10 pointer comparison",
},
{
"unpriv: check that printk is disallowed",
.insns = {
BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -8),
BPF_MOV64_IMM(BPF_REG_2, 8),
BPF_MOV64_REG(BPF_REG_3, BPF_REG_1),
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_trace_printk),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "unknown func 6",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
"unpriv: pass pointer to helper function",
.insns = {
BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
BPF_LD_MAP_FD(BPF_REG_1, 0),
BPF_MOV64_REG(BPF_REG_3, BPF_REG_2),
BPF_MOV64_REG(BPF_REG_4, BPF_REG_2),
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_update_elem),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.fixup = {3},
.errstr_unpriv = "R4 leaks addr",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
"unpriv: indirectly pass pointer on stack to helper function",
.insns = {
BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_10, -8),
BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
BPF_LD_MAP_FD(BPF_REG_1, 0),
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.fixup = {3},
.errstr = "invalid indirect read from stack off -8+0 size 8",
.result = REJECT,
},
{
"unpriv: mangle pointer on stack 1",
.insns = {
BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_10, -8),
BPF_ST_MEM(BPF_W, BPF_REG_10, -8, 0),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "attempt to corrupt spilled",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
"unpriv: mangle pointer on stack 2",
.insns = {
BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_10, -8),
BPF_ST_MEM(BPF_B, BPF_REG_10, -1, 0),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "attempt to corrupt spilled",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
"unpriv: read pointer from stack in small chunks",
.insns = {
BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_10, -8),
BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_10, -8),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr = "invalid size",
.result = REJECT,
},
{
"unpriv: write pointer into ctx",
.insns = {
BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, 0),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "R1 leaks addr",
.result_unpriv = REJECT,
.errstr = "invalid bpf_context access",
.result = REJECT,
},
{
"unpriv: write pointer into map elem value",
.insns = {
BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
BPF_LD_MAP_FD(BPF_REG_1, 0),
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
BPF_STX_MEM(BPF_DW, BPF_REG_0, BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.fixup = {3},
.errstr_unpriv = "R0 leaks addr",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
"unpriv: partial copy of pointer",
.insns = {
BPF_MOV32_REG(BPF_REG_1, BPF_REG_10),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "R10 partial copy",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
"unpriv: pass pointer to tail_call",
.insns = {
BPF_MOV64_REG(BPF_REG_3, BPF_REG_1),
BPF_LD_MAP_FD(BPF_REG_2, 0),
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_tail_call),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.prog_array_fixup = {1},
.errstr_unpriv = "R3 leaks addr into helper",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
"unpriv: cmp map pointer with zero",
.insns = {
BPF_MOV64_IMM(BPF_REG_1, 0),
BPF_LD_MAP_FD(BPF_REG_1, 0),
BPF_JMP_IMM(BPF_JEQ, BPF_REG_1, 0, 0),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.fixup = {1},
.errstr_unpriv = "R1 pointer comparison",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
"unpriv: write into frame pointer",
.insns = {
BPF_MOV64_REG(BPF_REG_10, BPF_REG_1),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr = "frame pointer is read only",
.result = REJECT,
},
{
"unpriv: cmp of frame pointer",
.insns = {
BPF_JMP_IMM(BPF_JEQ, BPF_REG_10, 0, 0),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "R10 pointer comparison",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
"unpriv: cmp of stack pointer",
.insns = {
BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
BPF_JMP_IMM(BPF_JEQ, BPF_REG_2, 0, 0),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "R2 pointer comparison",
.result_unpriv = REJECT,
.result = ACCEPT,
},
{
"unpriv: obfuscate stack pointer",
.insns = {
BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.errstr_unpriv = "R2 pointer arithmetic",
.result_unpriv = REJECT,
.result = ACCEPT,
},
};
static int probe_filter_length(struct bpf_insn *fp)
@ -896,13 +1195,24 @@ static int probe_filter_length(struct bpf_insn *fp)
static int create_map(void)
{
long long key, value = 0;
int map_fd;
map_fd = bpf_create_map(BPF_MAP_TYPE_HASH, sizeof(key), sizeof(value), 1024);
if (map_fd < 0) {
map_fd = bpf_create_map(BPF_MAP_TYPE_HASH,
sizeof(long long), sizeof(long long), 1024);
if (map_fd < 0)
printf("failed to create map '%s'\n", strerror(errno));
}
return map_fd;
}
static int create_prog_array(void)
{
int map_fd;
map_fd = bpf_create_map(BPF_MAP_TYPE_PROG_ARRAY,
sizeof(int), sizeof(int), 4);
if (map_fd < 0)
printf("failed to create prog_array '%s'\n", strerror(errno));
return map_fd;
}
@ -910,13 +1220,17 @@ static int create_map(void)
static int test(void)
{
int prog_fd, i, pass_cnt = 0, err_cnt = 0;
bool unpriv = geteuid() != 0;
for (i = 0; i < ARRAY_SIZE(tests); i++) {
struct bpf_insn *prog = tests[i].insns;
int prog_type = tests[i].prog_type;
int prog_len = probe_filter_length(prog);
int *fixup = tests[i].fixup;
int map_fd = -1;
int *prog_array_fixup = tests[i].prog_array_fixup;
int expected_result;
const char *expected_errstr;
int map_fd = -1, prog_array_fd = -1;
if (*fixup) {
map_fd = create_map();
@ -926,13 +1240,31 @@ static int test(void)
fixup++;
} while (*fixup);
}
if (*prog_array_fixup) {
prog_array_fd = create_prog_array();
do {
prog[*prog_array_fixup].imm = prog_array_fd;
prog_array_fixup++;
} while (*prog_array_fixup);
}
printf("#%d %s ", i, tests[i].descr);
prog_fd = bpf_prog_load(prog_type ?: BPF_PROG_TYPE_SOCKET_FILTER,
prog, prog_len * sizeof(struct bpf_insn),
"GPL", 0);
if (tests[i].result == ACCEPT) {
if (unpriv && tests[i].result_unpriv != UNDEF)
expected_result = tests[i].result_unpriv;
else
expected_result = tests[i].result;
if (unpriv && tests[i].errstr_unpriv)
expected_errstr = tests[i].errstr_unpriv;
else
expected_errstr = tests[i].errstr;
if (expected_result == ACCEPT) {
if (prog_fd < 0) {
printf("FAIL\nfailed to load prog '%s'\n",
strerror(errno));
@ -947,7 +1279,7 @@ static int test(void)
err_cnt++;
goto fail;
}
if (strstr(bpf_log_buf, tests[i].errstr) == 0) {
if (strstr(bpf_log_buf, expected_errstr) == 0) {
printf("FAIL\nunexpected error message: %s",
bpf_log_buf);
err_cnt++;
@ -960,6 +1292,8 @@ static int test(void)
fail:
if (map_fd >= 0)
close(map_fd);
if (prog_array_fd >= 0)
close(prog_array_fd);
close(prog_fd);
}
@ -970,5 +1304,8 @@ static int test(void)
int main(void)
{
struct rlimit r = {1 << 20, 1 << 20};
setrlimit(RLIMIT_MEMLOCK, &r);
return test();
}