From 63dfef75ed75364901d7caa52c6420cec3e73519 Mon Sep 17 00:00:00 2001 From: William Tu Date: Sat, 4 Feb 2017 08:37:29 -0800 Subject: [PATCH] bpf: enable verifier to add 0 to packet ptr The patch fixes the case when adding a zero value to the packet pointer. The zero value could come from src_reg equals type BPF_K or CONST_IMM. The patch fixes both, otherwise the verifer reports the following error: [...] R0=imm0,min_value=0,max_value=0 R1=pkt(id=0,off=0,r=4) R2=pkt_end R3=fp-12 R4=imm4,min_value=4,max_value=4 R5=pkt(id=0,off=4,r=4) 269: (bf) r2 = r0 // r2 becomes imm0 270: (77) r2 >>= 3 271: (bf) r4 = r1 // r4 becomes pkt ptr 272: (0f) r4 += r2 // r4 += 0 addition of negative constant to packet pointer is not allowed Signed-off-by: William Tu Signed-off-by: Mihai Budiu Cc: Daniel Borkmann Cc: Alexei Starovoitov Acked-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller --- kernel/bpf/verifier.c | 2 +- tools/testing/selftests/bpf/test_verifier.c | 23 +++++++++++++++++++++ 2 files changed, 24 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index fb3513b35c0b..1a754e5d2695 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1397,7 +1397,7 @@ static int check_packet_ptr_add(struct bpf_verifier_env *env, imm = insn->imm; add_imm: - if (imm <= 0) { + if (imm < 0) { verbose("addition of negative constant to packet pointer is not allowed\n"); return -EACCES; } diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index df194e1d56c2..71f6407cde60 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -2403,6 +2403,29 @@ static struct bpf_test tests[] = { .result = ACCEPT, .prog_type = BPF_PROG_TYPE_SCHED_CLS, }, + { + "direct packet access: test14 (pkt_ptr += 0, CONST_IMM, good access)", + .insns = { + BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, + offsetof(struct __sk_buff, data)), + BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1, + offsetof(struct __sk_buff, data_end)), + BPF_MOV64_REG(BPF_REG_0, BPF_REG_2), + BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, 22), + BPF_JMP_REG(BPF_JGT, BPF_REG_0, BPF_REG_3, 7), + BPF_MOV64_IMM(BPF_REG_5, 12), + BPF_ALU64_IMM(BPF_RSH, BPF_REG_5, 4), + BPF_MOV64_REG(BPF_REG_6, BPF_REG_2), + BPF_ALU64_REG(BPF_ADD, BPF_REG_6, BPF_REG_5), + BPF_LDX_MEM(BPF_B, BPF_REG_0, BPF_REG_6, 0), + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_EXIT_INSN(), + BPF_MOV64_IMM(BPF_REG_0, 0), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + .prog_type = BPF_PROG_TYPE_SCHED_CLS, + }, { "helper access to packet: test1, valid packet_ptr range", .insns = { -- 2.39.2