From: Gianluca Borello <g.bore...@gmail.com>
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.bore...@gmail.com>
Signed-off-by: Alexei Starovoitov <a...@kernel.org>
---
kernel/bpf/verifier.c | 9 ++++-
tools/testing/selftests/bpf/.gitignore | 1 +
tools/testing/selftests/bpf/test_verifier.c | 60 +++++++++++++++++++++++++++++
3 files changed, 68 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;
diff --git a/tools/testing/selftests/bpf/.gitignore
b/tools/testing/selftests/bpf/.gitignore
index 3c59f96e3ed8..071431bedde8 100644
--- a/tools/testing/selftests/bpf/.gitignore
+++ b/tools/testing/selftests/bpf/.gitignore
@@ -1,2 +1,3 @@
test_verifier
test_maps
+test_lru_map
diff --git a/tools/testing/selftests/bpf/test_verifier.c
b/tools/testing/selftests/bpf/test_verifier.c
index 5da2e9d7689c..8d71e44b319d 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -2683,6 +2683,66 @@ static struct bpf_test tests[] = {
.errstr_unpriv = "R0 pointer arithmetic prohibited",
.result_unpriv = REJECT,
},
+ {
+ "constant register |= constant should keep constant type",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -48),
+ BPF_MOV64_IMM(BPF_REG_2, 34),
+ BPF_ALU64_IMM(BPF_OR, BPF_REG_2, 13),
+ BPF_MOV64_IMM(BPF_REG_3, 0),
+ BPF_EMIT_CALL(BPF_FUNC_probe_read),
+ BPF_EXIT_INSN(),
+ },
+ .result = ACCEPT,
+ .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+ },
+ {
+ "constant register |= constant should not bypass stack boundary
checks",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -48),
+ BPF_MOV64_IMM(BPF_REG_2, 34),
+ BPF_ALU64_IMM(BPF_OR, BPF_REG_2, 24),
+ BPF_MOV64_IMM(BPF_REG_3, 0),
+ BPF_EMIT_CALL(BPF_FUNC_probe_read),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "invalid stack type R1 off=-48 access_size=58",
+ .result = REJECT,
+ .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+ },
+ {
+ "constant register |= constant register should keep constant
type",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -48),
+ BPF_MOV64_IMM(BPF_REG_2, 34),
+ BPF_MOV64_IMM(BPF_REG_4, 13),
+ BPF_ALU64_REG(BPF_OR, BPF_REG_2, BPF_REG_4),
+ BPF_MOV64_IMM(BPF_REG_3, 0),
+ BPF_EMIT_CALL(BPF_FUNC_probe_read),
+ BPF_EXIT_INSN(),
+ },
+ .result = ACCEPT,
+ .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+ },
+ {
+ "constant register |= constant register should not bypass stack
boundary checks",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -48),
+ BPF_MOV64_IMM(BPF_REG_2, 34),
+ BPF_MOV64_IMM(BPF_REG_4, 24),
+ BPF_ALU64_REG(BPF_OR, BPF_REG_2, BPF_REG_4),
+ BPF_MOV64_IMM(BPF_REG_3, 0),
+ BPF_EMIT_CALL(BPF_FUNC_probe_read),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "invalid stack type R1 off=-48 access_size=58",
+ .result = REJECT,
+ .prog_type = BPF_PROG_TYPE_TRACEPOINT,
+ },
};
static int probe_filter_length(const struct bpf_insn *fp)
--
2.8.0
