[PATCH bpf-next v3 3/3] selftests/bpf: Cover commuted pointer state propagation

[Yiyang Chen]

Add verifier coverage for the three cases affected by preserving the full
pointer state across scalar += pointer: stack frame number inheritance,
readonly-untrusted memory access, and dynptr data-slice invalidation.

Signed-off-by: Yiyang Chen <chenyy23@xxxxxxxxxxxxxxxxxxxxx>
---
 .../testing/selftests/bpf/progs/dynptr_fail.c | 31 ++++++++++++++
 .../bpf/progs/mem_rdonly_untrusted.c          | 17 ++++++++
 .../bpf/progs/verifier_basic_stack.c          | 41 +++++++++++++++++++
 3 files changed, 89 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c
index 94489ac64da8e..7da4266bae09b 100644
--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c
+++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c
@@ -1635,6 +1635,37 @@ static int callback(__u32 index, void *data)
         return 0;
 }
 
+/* A commuted add should preserve the parent id of a dynptr data slice.
+ */
+SEC("?raw_tp")
+__failure __msg("invalid mem access 'scalar'")
+int dynptr_slice_commuted_invalidate(void *ctx)
+{
+	struct bpf_dynptr ptr;
+	__u32 *slice, *derived;
+
+	bpf_ringbuf_reserve_dynptr(&ringbuf, sizeof(__u32), 0, &ptr);
+
+	slice = bpf_dynptr_data(&ptr, 0, sizeof(__u32));
+	if (!slice)
+		goto done;
+
+	asm volatile ("%[dst] = 0;"
+		"%[dst] += %[src];"
+		"%[src] = 0;"
+		: [dst]"=&r"(derived), [src]"+r"(slice)
+		:
+		: "memory");
+
+	bpf_ringbuf_discard_dynptr(&ptr, 0);
+	val = *derived;
+	return 0;
+
+done:
+	bpf_ringbuf_discard_dynptr(&ptr, 0);
+	return 0;
+}
+
 /* If the dynptr is written into in a callback function, its data
  * slices should be invalidated as well.
  */
diff --git a/tools/testing/selftests/bpf/progs/mem_rdonly_untrusted.c b/tools/testing/selftests/bpf/progs/mem_rdonly_untrusted.c
index 5b4453747c230..f166fff8f2176 100644
--- a/tools/testing/selftests/bpf/progs/mem_rdonly_untrusted.c
+++ b/tools/testing/selftests/bpf/progs/mem_rdonly_untrusted.c
@@ -226,4 +226,21 @@ int null_check(void *ctx)
 	return 0;
 }
 
+SEC("socket")
+__success
+__retval(1)
+int ldx_is_ok_commuted_addr(void *ctx)
+{
+	int v, *p, *derived;
+
+	v = 1;
+	p = bpf_rdonly_cast(&v, 0);
+	asm volatile ("%[dst] = 0;"
+		"%[dst] += %[src];"
+		: [dst]"=&r"(derived)
+		: [src]"r"(p)
+		: "memory");
+	return *derived;
+}
+
 char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/verifier_basic_stack.c b/tools/testing/selftests/bpf/progs/verifier_basic_stack.c
index fb62e09f21146..d3df7a9f1d8c8 100644
--- a/tools/testing/selftests/bpf/progs/verifier_basic_stack.c
+++ b/tools/testing/selftests/bpf/progs/verifier_basic_stack.c
@@ -97,4 +97,45 @@ __naked void misaligned_read_from_stack(void)
 "	::: __clobber_all);
 }
 
+SEC("socket")
+__description("stack pointer arithmetic preserves frame number")
+__failure __msg("R7 invalid mem access 'scalar'")
+__naked void stack_ptr_arith_preserves_frameno(void)
+{
+	asm volatile ("\
+		r3 = 0;						\
+		*(u64 *)(r10 - 8) = r3;			\
+		r1 = %[map_hash_8b] ll;			\
+		r2 = r10;					\
+		r2 += -8;					\
+		call %[bpf_map_lookup_elem];		\
+		if r0 != 0 goto +2;			\
+		r0 = 0;						\
+		exit;						\
+		r1 = r0;					\
+		r2 = 0;						\
+		r3 = 0;						\
+		call stack_ptr_arith_preserves_frameno_subprog;\
+		r0 = 0;						\
+		exit;						\
+	":
+	: __imm(bpf_map_lookup_elem),
+	  __imm_addr(map_hash_8b)
+	: __clobber_all);
+}
+
+static __used __naked void stack_ptr_arith_preserves_frameno_subprog(void)
+{
+	asm volatile ("\
+		*(u64 *)(r10 - 8) = r1;			\
+		r6 = -8;					\
+		r6 += r10;					\
+		*(u64 *)(r6 + 0) = r2;			\
+		r7 = *(u64 *)(r10 - 8);			\
+		*(u64 *)(r7 + 0) = r3;			\
+		r0 = 0;						\
+		exit;						\
+	"::: __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.34.1