[bpf-next PATCH v2 6/7] bpf: test_verifier, #65 error message updates for trunc of boundary-cross
From: John Fastabend <john.fastabend@gmail.com>
Date: 2020-03-30 21:38:17
Also in:
bpf
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Linus Torvalds
After changes to add update_reg_bounds after ALU ops and 32-bit bounds
tracking truncation of boundary crossing range will fail earlier and with
a different error message. Now the test error trace is the following
11: (17) r1 -= 2147483584
12: R0_w=map_value(id=0,off=0,ks=8,vs=8,imm=0)
R1_w=invP(id=0,smin_value=-2147483584,smax_value=63)
R10=fp0 fp-8_w=mmmmmmmm
12: (17) r1 -= 2147483584
13: R0_w=map_value(id=0,off=0,ks=8,vs=8,imm=0)
R1_w=invP(id=0,
umin_value=18446744069414584448,umax_value=18446744071562068095,
var_off=(0xffffffff00000000; 0xffffffff))
R10=fp0 fp-8_w=mmmmmmmm
13: (77) r1 >>= 8
14: R0_w=map_value(id=0,off=0,ks=8,vs=8,imm=0)
R1_w=invP(id=0,
umin_value=72057594021150720,umax_value=72057594029539328,
var_off=(0xffffffff000000; 0xffffff),
s32_min_value=-16777216,s32_max_value=-1,
u32_min_value=-16777216)
R10=fp0 fp-8_w=mmmmmmmm
14: (0f) r0 += r1
value 72057594021150720 makes map_value pointer be out of bounds
Because we have 'umin_value == umax_value' instead of previously
where 'umin_value != umax_value' we can now fail earlier noting
that pointer addition is out of bounds.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
---
tools/testing/selftests/bpf/verifier/bounds.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/tools/testing/selftests/bpf/verifier/bounds.c b/tools/testing/selftests/bpf/verifier/bounds.c
index 7c9b659..cf72fcc 100644
--- a/tools/testing/selftests/bpf/verifier/bounds.c
+++ b/tools/testing/selftests/bpf/verifier/bounds.c@@ -257,17 +257,15 @@ * [0x00ff'ffff'ff00'0000, 0x00ff'ffff'ffff'ffff] */ BPF_ALU64_IMM(BPF_RSH, BPF_REG_1, 8), - /* no-op or OOB pointer computation */ + /* error on OOB pointer computation */ BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1), - /* potentially OOB access */ - BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_0, 0), /* exit */ BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, .fixup_map_hash_8b = { 3 }, /* not actually fully unbounded, but the bound is very high */ - .errstr = "R0 unbounded memory access", + .errstr = "value 72057594021150720 makes map_value pointer be out of bounds", .result = REJECT }, {
@@ -299,17 +297,15 @@ * [0x00ff'ffff'ff00'0000, 0x00ff'ffff'ffff'ffff] */ BPF_ALU64_IMM(BPF_RSH, BPF_REG_1, 8), - /* no-op or OOB pointer computation */ + /* error on OOB pointer computation */ BPF_ALU64_REG(BPF_ADD, BPF_REG_0, BPF_REG_1), - /* potentially OOB access */ - BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_0, 0), /* exit */ BPF_MOV64_IMM(BPF_REG_0, 0), BPF_EXIT_INSN(), }, .fixup_map_hash_8b = { 3 }, /* not actually fully unbounded, but the bound is very high */ - .errstr = "R0 unbounded memory access", + .errstr = "value 72057594021150720 makes map_value pointer be out of bounds", .result = REJECT }, {