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authorGianluca Borello <g.borello@gmail.com>2016-12-03 12:31:33 -0800
committerDavid S. Miller <davem@davemloft.net>2016-12-05 13:40:05 -0500
commit3c839744b33782b930c5c61df35511ede5e5a574 (patch)
tree950a0b8dd43c23f87e636bacd3074a5076818d93 /kernel/bpf
parentf0903ea371f56c4977d1c07c2f8d4a55846c2801 (diff)
downloadlinux-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.c9
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 = &regs[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;