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selftests/bpf: add test for bogus operations on pointers

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Tests non-add/sub operations (AND, LSH) on pointers decaying them to
 unknown scalars.
Also tests that a pkt_ptr add which could potentially overflow is rejected
 (find_good_pkt_pointers ignores it and doesn't give us any reg->range).

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Edward Cree 2017-08-07 15:28:45 +01:00 committed by David S. Miller
parent 715dddb5e6
commit c2c3e11712
1 changed files with 64 additions and 2 deletions
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66
tools/testing/selftests/bpf/test_align.c
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@ -441,6 +441,62 @@ static struct bpf_align_test tests[] = {
{23, "R5=pkt(id=2,off=0,r=4,umin_value=14,umax_value=2054,var_off=(0x2; 0xffc))"},
},
},
{
.descr = "dubious pointer arithmetic",
.insns = {
PREP_PKT_POINTERS,
BPF_MOV64_IMM(BPF_REG_0, 0),
/* ptr & const => unknown & const */
BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
BPF_ALU64_IMM(BPF_AND, BPF_REG_5, 0x40),
/* ptr << const => unknown << const */
BPF_MOV64_REG(BPF_REG_5, BPF_REG_2),
BPF_ALU64_IMM(BPF_LSH, BPF_REG_5, 2),
/* We have a (4n) value. Let's make a packet offset
* out of it. First add 14, to make it a (4n+2)
*/
BPF_ALU64_IMM(BPF_ADD, BPF_REG_5, 14),
/* Then make sure it's nonnegative */
BPF_JMP_IMM(BPF_JSGE, BPF_REG_5, 0, 1),
BPF_EXIT_INSN(),
/* Add it to packet pointer */
BPF_MOV64_REG(BPF_REG_6, BPF_REG_2),
BPF_ALU64_REG(BPF_ADD, BPF_REG_6, BPF_REG_5),
/* Check bounds and perform a read */
BPF_MOV64_REG(BPF_REG_4, BPF_REG_6),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_4, 4),
BPF_JMP_REG(BPF_JGE, BPF_REG_3, BPF_REG_4, 1),
BPF_EXIT_INSN(),
BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_6, 0),
BPF_EXIT_INSN(),
},
.prog_type = BPF_PROG_TYPE_SCHED_CLS,
.result = REJECT,
.matches = {
{4, "R5=pkt(id=0,off=0,r=0,imm=0)"},
/* ptr & 0x40 == either 0 or 0x40 */
{5, "R5=inv(id=0,umax_value=64,var_off=(0x0; 0x40))"},
/* ptr << 2 == unknown, (4n) */
{7, "R5=inv(id=0,smax_value=9223372036854775804,umax_value=18446744073709551612,var_off=(0x0; 0xfffffffffffffffc))"},
/* (4n) + 14 == (4n+2). We blow our bounds, because
* the add could overflow.
*/
{8, "R5=inv(id=0,var_off=(0x2; 0xfffffffffffffffc))"},
/* Checked s>=0 */
{10, "R5=inv(id=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
/* packet pointer + nonnegative (4n+2) */
{12, "R6=pkt(id=1,off=0,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
{14, "R4=pkt(id=1,off=4,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
/* NET_IP_ALIGN + (4n+2) == (4n), alignment is fine.
* We checked the bounds, but it might have been able
* to overflow if the packet pointer started in the
* upper half of the address space.
* So we did not get a 'range' on R6, and the access
* attempt will fail.
*/
{16, "R6=pkt(id=1,off=0,r=0,umin_value=2,umax_value=9223372036854775806,var_off=(0x2; 0x7ffffffffffffffc))"},
}
},
};
static int probe_filter_length(const struct bpf_insn *fp)
@ -470,10 +526,15 @@ static int do_test_single(struct bpf_align_test *test)
fd_prog = bpf_verify_program(prog_type ? : BPF_PROG_TYPE_SOCKET_FILTER,
prog, prog_len, 1, "GPL", 0,
bpf_vlog, sizeof(bpf_vlog), 2);
if (fd_prog < 0) {
if (fd_prog < 0 && test->result != REJECT) {
printf("Failed to load program.\n");
printf("%s", bpf_vlog);
ret = 1;
} else if (fd_prog >= 0 && test->result == REJECT) {
printf("Unexpected success to load!\n");
printf("%s", bpf_vlog);
ret = 1;
close(fd_prog);
} else {
ret = 0;
/* We make a local copy so that we can strtok() it */
@ -506,7 +567,8 @@ static int do_test_single(struct bpf_align_test *test)
break;
}
}
close(fd_prog);
if (fd_prog >= 0)
close(fd_prog);
}
return ret;
}