diff options
| author | Gianluca Borello <g.borello@gmail.com> | 2016-12-03 12:31:33 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-12-05 13:40:05 -0500 |
| commit | 3c839744b33782b930c5c61df35511ede5e5a574 (patch) | |
| tree | 950a0b8dd43c23f87e636bacd3074a5076818d93 /kernel/bpf | |
| parent | f0903ea371f56c4977d1c07c2f8d4a55846c2801 (diff) | |
| download | linux-3c839744b33782b930c5c61df35511ede5e5a574.tar.gz | |
bpf: Preserve const register type on const OR alu ops
Occasionally, clang (e.g. version 3.8.1) translates a sum between two
constant operands using a BPF_OR instead of a BPF_ADD. The verifier is
currently not handling this scenario, and the destination register type
becomes UNKNOWN_VALUE even if it's still storing a constant. As a result,
the destination register cannot be used as argument to a helper function
expecting a ARG_CONST_STACK_*, limiting some use cases.
Modify the verifier to handle this case, and add a few tests to make sure
all combinations are supported, and stack boundaries are still verified
even with BPF_OR.
Signed-off-by: Gianluca Borello <g.borello@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/verifier.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 0e742210750e..38d05da84a49 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1481,14 +1481,19 @@ static int evaluate_reg_imm_alu(struct bpf_verifier_env *env, struct bpf_reg_state *src_reg = ®s[insn->src_reg]; u8 opcode = BPF_OP(insn->code); - /* dst_reg->type == CONST_IMM here, simulate execution of 'add' insn. - * Don't care about overflow or negative values, just add them + /* dst_reg->type == CONST_IMM here, simulate execution of 'add'/'or' + * insn. Don't care about overflow or negative values, just add them */ if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_K) dst_reg->imm += insn->imm; else if (opcode == BPF_ADD && BPF_SRC(insn->code) == BPF_X && src_reg->type == CONST_IMM) dst_reg->imm += src_reg->imm; + else if (opcode == BPF_OR && BPF_SRC(insn->code) == BPF_K) + dst_reg->imm |= insn->imm; + else if (opcode == BPF_OR && BPF_SRC(insn->code) == BPF_X && + src_reg->type == CONST_IMM) + dst_reg->imm |= src_reg->imm; else mark_reg_unknown_value(regs, insn->dst_reg); return 0; |