selftests/bpf: Add test for reading from STACK_INVALID slots

Ensure that when CAP_PERFMON is dropped, and the verifier sees
allow_ptr_leaks as false, we are not permitted to read from a
STACK_INVALID slot. Without the fix, the test will report unexpected
success in loading.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20241204044757.1483141-5-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
index 671d9f415dbf7b041ef20f38f308b30f92ea979c..bab6d789ba007b0655e1d84fcac56bfb0448775f 100644 (file)
--- a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
+++ b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
@@ -1244,4 +1244,22 @@ __naked void old_stack_misc_vs_cur_ctx_ptr(void)
        : __clobber_all);
 }
 
+SEC("socket")
+__description("stack_noperfmon: reject read of invalid slots")
+__success
+__caps_unpriv(CAP_BPF)
+__failure_unpriv __msg_unpriv("invalid read from stack off -8+1 size 8")
+__naked void stack_noperfmon_reject_invalid_read(void)
+{
+       asm volatile ("                                 \
+       r2 = 1;                                         \
+       r6 = r10;                                       \
+       r6 += -8;                                       \
+       *(u8 *)(r6 + 0) = r2;                           \
+       r2 = *(u64 *)(r6 + 0);                          \
+       r0 = 0;                                         \
+       exit;                                           \
+"      ::: __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";