4.14-stable review patch. If anyone has any objections, please let me know.
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From: Daniel Borkmann daniel@iogearbox.net
commit 7891a87efc7116590eaba57acc3c422487802c6f upstream.
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 daniel@iogearbox.net Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/bpf/verifier.c | 5 +++ tools/testing/selftests/bpf/test_verifier.c | 40 ++++++++++++++++++++++++++++ 2 files changed, 45 insertions(+)
--- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2493,6 +2493,11 @@ static int check_alu_op(struct bpf_verif return -EINVAL; }
+ if (opcode == BPF_ARSH && BPF_CLASS(insn->code) != BPF_ALU64) { + verbose("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; --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -273,6 +273,46 @@ static struct bpf_test tests[] = { .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 = { BPF_ALU64_REG(BPF_MOV, BPF_REG_0, BPF_REG_2),