From 7891a87efc7116590eaba57acc3c422487802c6f Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Wed, 10 Jan 2018 20:04:37 +0100 Subject: [PATCH] bpf: arsh is not supported in 32 bit alu thus reject it The following snippet was throwing an 'unknown opcode cc' warning in BPF interpreter: 0: (18) r0 = 0x0 2: (7b) *(u64 *)(r10 -16) = r0 3: (cc) (u32) r0 s>>= (u32) r0 4: (95) exit Although a number of JITs do support BPF_ALU | BPF_ARSH | BPF_{K,X} generation, not all of them do and interpreter does neither. We can leave existing ones and implement it later in bpf-next for the remaining ones, but reject this properly in verifier for the time being. Fixes: 17a5267067f3 ("bpf: verifier (add verifier core)") Reported-by: syzbot+93c4904c5c70348a6890@syzkaller.appspotmail.com Signed-off-by: Daniel Borkmann Signed-off-by: Alexei Starovoitov --- kernel/bpf/verifier.c | 5 +++ tools/testing/selftests/bpf/test_verifier.c | 40 +++++++++++++++++++++ 2 files changed, 45 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 96ab165c873c..20eb04fd155e 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2493,6 +2493,11 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn) return -EINVAL; } + if (opcode == BPF_ARSH && BPF_CLASS(insn->code) != BPF_ALU64) { + verbose(env, "BPF_ARSH not supported for 32 bit ALU\n"); + return -EINVAL; + } + if ((opcode == BPF_LSH || opcode == BPF_RSH || opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) { int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32; diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index b51017404c62..6bafa5456568 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -272,6 +272,46 @@ static struct bpf_test tests[] = { .errstr = "invalid bpf_ld_imm64 insn", .result = REJECT, }, + { + "arsh32 on imm", + .insns = { + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_ALU32_IMM(BPF_ARSH, BPF_REG_0, 5), + BPF_EXIT_INSN(), + }, + .result = REJECT, + .errstr = "BPF_ARSH not supported for 32 bit ALU", + }, + { + "arsh32 on reg", + .insns = { + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_MOV64_IMM(BPF_REG_1, 5), + BPF_ALU32_REG(BPF_ARSH, BPF_REG_0, BPF_REG_1), + BPF_EXIT_INSN(), + }, + .result = REJECT, + .errstr = "BPF_ARSH not supported for 32 bit ALU", + }, + { + "arsh64 on imm", + .insns = { + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_ALU64_IMM(BPF_ARSH, BPF_REG_0, 5), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + }, + { + "arsh64 on reg", + .insns = { + BPF_MOV64_IMM(BPF_REG_0, 1), + BPF_MOV64_IMM(BPF_REG_1, 5), + BPF_ALU64_REG(BPF_ARSH, BPF_REG_0, BPF_REG_1), + BPF_EXIT_INSN(), + }, + .result = ACCEPT, + }, { "no bpf_exit", .insns = { -- 2.30.2