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 <[email protected]>
kernel-patches · Dec 2, 2024 · 0637ae3 · 0637ae3
1 parent ffcd4fd
commit 0637ae3
Showing 1 changed file with 17 additions and 0 deletions.
diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
@@ -1244,4 +1244,21 @@ __naked void old_stack_misc_vs_cur_ctx_ptr(void)
 	: __clobber_all);
 }
 
+SEC("tc")
+__description("stack_noperfmon: reject read of invalid slots")
+__success __failure_unpriv __msg_unpriv("invalid read from stack off -8+1 size 8")
+__caps_unpriv(CAP_BPF)
+__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";