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authorYonghong Song <yhs@fb.com>2017-04-29 22:52:42 -0700
committerDavid S. Miller <davem@davemloft.net>2017-05-01 11:40:23 -0400
commit332270fdc8b6fba07d059a9ad44df9e1a2ad4529 (patch)
tree95e4cf412f1691c5ac9063c64989337fc80a278e /tools
parent2faf26575350e49c1e242b7a464e9302f78b9b15 (diff)
bpf: enhance verifier to understand stack pointer arithmetic
llvm 4.0 and above generates the code like below: .... 440: (b7) r1 = 15 441: (05) goto pc+73 515: (79) r6 = *(u64 *)(r10 -152) 516: (bf) r7 = r10 517: (07) r7 += -112 518: (bf) r2 = r7 519: (0f) r2 += r1 520: (71) r1 = *(u8 *)(r8 +0) 521: (73) *(u8 *)(r2 +45) = r1 .... and the verifier complains "R2 invalid mem access 'inv'" for insn #521. This is because verifier marks register r2 as unknown value after #519 where r2 is a stack pointer and r1 holds a constant value. Teach verifier to recognize "stack_ptr + imm" and "stack_ptr + reg with const val" as valid stack_ptr with new offset. Signed-off-by: Yonghong Song <yhs@fb.com> Acked-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-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.c18
1 files changed, 12 insertions, 6 deletions
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index d3395c192a24..3773562056da 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -1932,16 +1932,22 @@ static struct bpf_test tests[] = {
.result = ACCEPT,
},
{
- "unpriv: obfuscate stack pointer",
+ "stack pointer arithmetic",
.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_1, 4),
+ BPF_JMP_IMM(BPF_JA, 0, 0, 0),
+ BPF_MOV64_REG(BPF_REG_7, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, -10),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_7),
+ BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_1),
+ BPF_ST_MEM(0, BPF_REG_2, 4, 0),
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_7),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, 8),
+ BPF_ST_MEM(0, BPF_REG_2, 4, 0),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
- .errstr_unpriv = "R2 pointer arithmetic",
- .result_unpriv = REJECT,
.result = ACCEPT,
},
{