bpf: allow adjusted map element values to spill
commit 484611357c19 ("bpf: allow access into map value arrays")
introduces the ability to do pointer math inside a map element value via
the PTR_TO_MAP_VALUE_ADJ register type.
The current support doesn't handle the case where a PTR_TO_MAP_VALUE_ADJ
is spilled into the stack, limiting several use cases, especially when
generating bpf code from a compiler.
Handle this case by explicitly enabling the register type
PTR_TO_MAP_VALUE_ADJ to be spilled. Also, make sure that min_value and
max_value are reset just for BPF_LDX operations that don't result in a
restore of a spilled register from stack.
Signed-off-by: Gianluca Borello <g.borello@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index b7732e5..e7b0758 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -3396,6 +3396,52 @@ static struct bpf_test tests[] = {
.result = REJECT,
.prog_type = BPF_PROG_TYPE_TRACEPOINT,
},
+ {
+ "map element value is preserved across register spilling",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+ BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 6),
+ BPF_ST_MEM(BPF_DW, BPF_REG_0, 0, 42),
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -184),
+ BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0, 0),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_3, BPF_REG_1, 0),
+ BPF_ST_MEM(BPF_DW, BPF_REG_3, 0, 42),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map2 = { 3 },
+ .errstr_unpriv = "R0 leaks addr",
+ .result = ACCEPT,
+ .result_unpriv = REJECT,
+ },
+ {
+ "map element value (adjusted) is preserved across register spilling",
+ .insns = {
+ BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -8),
+ BPF_ST_MEM(BPF_DW, BPF_REG_2, 0, 0),
+ BPF_LD_MAP_FD(BPF_REG_1, 0),
+ BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
+ BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 7),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_0,
+ offsetof(struct test_val, foo)),
+ BPF_ST_MEM(BPF_DW, BPF_REG_0, 0, 42),
+ BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
+ BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -184),
+ BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0, 0),
+ BPF_LDX_MEM(BPF_DW, BPF_REG_3, BPF_REG_1, 0),
+ BPF_ST_MEM(BPF_DW, BPF_REG_3, 0, 42),
+ BPF_EXIT_INSN(),
+ },
+ .fixup_map2 = { 3 },
+ .errstr_unpriv = "R0 pointer arithmetic prohibited",
+ .result = ACCEPT,
+ .result_unpriv = REJECT,
+ },
};
static int probe_filter_length(const struct bpf_insn *fp)