diff options
| author | Edward Cree | 2017-08-23 15:09:46 +0100 |
|---|---|---|
| committer | David S. Miller | 2017-08-23 22:38:07 -0700 |
| commit | d893dc26e3f42e12ae75703c52cc6de5578ff1f5 (patch) | |
| tree | bc1f40ad9367a4462f4c917d722958b165bfeea6 /tools | |
| parent | 60890e046081aef61980dbc812ac5100ad078a87 (diff) | |
selftests/bpf: add a test for a bug in liveness-based pruning
Writes in straight-line code should not prevent reads from propagating
along jumps. With current verifier code, the jump from 3 to 5 does not
add a read mark on 3:R0 (because 5:R0 has a write mark), meaning that
the jump from 1 to 3 gets pruned as safe even though R0 is NOT_INIT.
Verifier output:
0: (61) r2 = *(u32 *)(r1 +0)
1: (35) if r2 >= 0x0 goto pc+1
R1=ctx(id=0,off=0,imm=0) R2=inv(id=0,umax_value=4294967295,var_off=(0x0; 0xffffffff)) R10=fp0
2: (b7) r0 = 0
3: (35) if r2 >= 0x0 goto pc+1
R0=inv0 R1=ctx(id=0,off=0,imm=0) R2=inv(id=0,umax_value=4294967295,var_off=(0x0; 0xffffffff)) R10=fp0
4: (b7) r0 = 0
5: (95) exit
from 3 to 5: safe
from 1 to 3: safe
processed 8 insns, stack depth 0
Signed-off-by: Edward Cree <ecree@solarflare.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/testing/selftests/bpf/test_verifier.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index c03542c417db..c912734d2364 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -6487,6 +6487,22 @@ static struct bpf_test tests[] = { .result = REJECT, .prog_type = BPF_PROG_TYPE_LWT_IN, }, + { + "liveness pruning and write screening", + .insns = { + /* Get an unknown value */ + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0), + /* branch conditions teach us nothing about R2 */ + BPF_JMP_IMM(BPF_JGE, BPF_REG_2, 0, 1), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_JMP_IMM(BPF_JGE, BPF_REG_2, 0, 1), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .errstr = "R0 !read_ok", + .result = REJECT, + .prog_type = BPF_PROG_TYPE_LWT_IN, + }, }; static int probe_filter_length(const struct bpf_insn *fp) |