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authorAlexei Starovoitov <ast@kernel.org>2018-12-03 22:46:05 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2018-12-04 17:22:02 +0100
commit4f7b3e82589e0de723780198ec7983e427144c0a (patch)
tree38fa3a5035551cfe6b4e5d7d5268ca4834e353f5 /tools
parentc3494801cd1785e2c25f1a5735fa19ddcf9665da (diff)
downloadlinux-4f7b3e82589e0de723780198ec7983e427144c0a.tar.bz2
bpf: improve verifier branch analysis
pathological bpf programs may try to force verifier to explode in the number of branch states: 20: (d5) if r1 s<= 0x24000028 goto pc+0 21: (b5) if r0 <= 0xe1fa20 goto pc+2 22: (d5) if r1 s<= 0x7e goto pc+0 23: (b5) if r0 <= 0xe880e000 goto pc+0 24: (c5) if r0 s< 0x2100ecf4 goto pc+0 25: (d5) if r1 s<= 0xe880e000 goto pc+1 26: (c5) if r0 s< 0xf4041810 goto pc+0 27: (d5) if r1 s<= 0x1e007e goto pc+0 28: (b5) if r0 <= 0xe86be000 goto pc+0 29: (07) r0 += 16614 30: (c5) if r0 s< 0x6d0020da goto pc+0 31: (35) if r0 >= 0x2100ecf4 goto pc+0 Teach verifier to recognize always taken and always not taken branches. This analysis is already done for == and != comparison. Expand it to all other branches. It also helps real bpf programs to be verified faster: before after bpf_lb-DLB_L3.o 2003 1940 bpf_lb-DLB_L4.o 3173 3089 bpf_lb-DUNKNOWN.o 1080 1065 bpf_lxc-DDROP_ALL.o 29584 28052 bpf_lxc-DUNKNOWN.o 36916 35487 bpf_netdev.o 11188 10864 bpf_overlay.o 6679 6643 bpf_lcx_jit.o 39555 38437 Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Edward Cree <ecree@solarflare.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'tools')
-rw-r--r--tools/testing/selftests/bpf/test_verifier.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 5dd4410a716c..df6f751cc1e8 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -8576,7 +8576,7 @@ static struct bpf_test tests[] = {
BPF_JMP_IMM(BPF_JA, 0, 0, -7),
},
.fixup_map_hash_8b = { 4 },
- .errstr = "R0 invalid mem access 'inv'",
+ .errstr = "unbounded min value",
.result = REJECT,
},
{
@@ -10547,7 +10547,7 @@ static struct bpf_test tests[] = {
"check deducing bounds from const, 5",
.insns = {
BPF_MOV64_IMM(BPF_REG_0, 0),
- BPF_JMP_IMM(BPF_JSGE, BPF_REG_0, 0, 1),
+ BPF_JMP_IMM(BPF_JSGE, BPF_REG_0, 1, 1),
BPF_ALU64_REG(BPF_SUB, BPF_REG_0, BPF_REG_1),
BPF_EXIT_INSN(),
},