Test that verifier rejects indirect access to uninitialized stack with
variable offset.
Example of output:
# ./test_verifier
...
#859/p indirect variable-offset stack access, uninitialized OK
Signed-off-by: Andrey Ignatov <r...@fb.com>
---
.../testing/selftests/bpf/verifier/var_off.c | 27 +++++++++++++++++++
1 file changed, 27 insertions(+)
diff --git a/tools/testing/selftests/bpf/verifier/var_off.c
b/tools/testing/selftests/bpf/verifier/var_off.c
index c4ebd0bb0781..7d095bd04636 100644
--- a/tools/testing/selftests/bpf/verifier/var_off.c
+++ b/tools/testing/selftests/bpf/verifier/var_off.c
@@ -114,6 +114,33 @@
.result = REJECT,
.prog_type = BPF_PROG_TYPE_LWT_IN,
},
+{
+ "indirect variable-offset stack access, uninitialized",
+ .insns = {
+ BPF_MOV64_IMM(BPF_REG_2, 6),
+ BPF_MOV64_IMM(BPF_REG_3, 28),
+ /* Fill the top 16 bytes of the stack. */
+ BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 0),
+ BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+ /* Get an unknown value. */
+ BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_1, 0),
+ /* Make it small and 4-byte aligned. */
+ BPF_ALU64_IMM(BPF_AND, BPF_REG_4, 4),
+ BPF_ALU64_IMM(BPF_SUB, BPF_REG_4, 16),
+ /* Add it to fp. We now have either fp-12 or fp-16, we don't know
+ * which, but either way it points to initialized stack.
+ */
+ BPF_ALU64_REG(BPF_ADD, BPF_REG_4, BPF_REG_10),
+ BPF_MOV64_IMM(BPF_REG_5, 8),
+ /* Dereference it indirectly. */
+ BPF_EMIT_CALL(BPF_FUNC_getsockopt),
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ },
+ .errstr = "R4 invalid indirect access to uninitialized stack var_off=",
+ .result = REJECT,
+ .prog_type = BPF_PROG_TYPE_SOCK_OPS,
+},
{
"indirect variable-offset stack access, ok",
.insns = {
--
2.17.1
