selftests/bpf: precision of a NULL helper argument

Check that mark_chain_precision() is called for a NULL nullable memory
argument and for the zero flags argument of bpf_get_local_storage().

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-2-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 63 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/verifier_cgroup_storage.c b/tools/testing/selftests/bpf/progs/verifier_cgroup_storage.c
index 9a13f5c11ac7..884080a5bffc 100644
--- a/tools/testing/selftests/bpf/progs/verifier_cgroup_storage.c
+++ b/tools/testing/selftests/bpf/progs/verifier_cgroup_storage.c
@@ -305,4 +305,33 @@ __naked void cpu_cgroup_storage_access_6(void)
 	: __clobber_all);
 }
 
+/*
+ * Verification takes two paths: with r2 being scalar zero on path (1)
+ * and with r2 being some other scalar on path (2).
+ * Check that the verifier does not use checkpoints created
+ * on path (1) to prune path (2).
+ */
+SEC("cgroup/skb")
+__failure
+__flag(BPF_F_TEST_STATE_FREQ)
+__msg("get_local_storage() doesn't support non-zero flags")
+__naked void non_zero_flags_on_a_pruned_path(void)
+{
+	asm volatile ("					\
+	call %[bpf_get_prandom_u32];			\
+	/* r2 is 0 on the path explored first, 1 on the other */\
+	r2 = 1;						\
+	if r0 == 0 goto 1f;				\
+	r2 = 0;						\
+1:	r1 = %[cgroup_storage] ll;			\
+	call %[bpf_get_local_storage];			\
+	r0 = 0;						\
+	exit;						\
+"	:
+	: __imm(bpf_get_prandom_u32),
+	  __imm(bpf_get_local_storage),
+	  __imm_addr(cgroup_storage)
+	: __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/verifier_precision.c b/tools/testing/selftests/bpf/progs/verifier_precision.c
index 6f325876efdd..3e290b07f672 100644
--- a/tools/testing/selftests/bpf/progs/verifier_precision.c
+++ b/tools/testing/selftests/bpf/progs/verifier_precision.c
@@ -642,4 +642,38 @@ __naked int bpf_atomic_cmpxchg_32bit_precision(void)
 	: __clobber_all);
 }
 
+/*
+ * Verification takes two paths: with r1 being scalar zero on path (1)
+ * and with r1 being some other scalar on path (2).
+ * Check that the verifier does not use checkpoints created
+ * on path (1) to prune path (2).
+ */
+SEC("?tc")
+__flag(BPF_F_TEST_STATE_FREQ)
+__failure __msg("R1 type=scalar expected=fp")
+__naked int null_mem_arg_zero_size(void)
+{
+	asm volatile (
+		"call %[bpf_get_prandom_u32];"
+		"r1 = 42;"
+		"if r0 > 42 goto 1f;"
+		"r1 = 0;"
+	"1:"
+		"r2 = 0;"
+		"r3 = 0;"
+		"r4 = 0;"
+		"r5 = 0;"
+		/*
+		 * ARG_PTR_TO_MEM | PTR_MAYBE_NULL parameter can be NULL,
+		 * but can't be some other scalar value.
+		 */
+		"call %[bpf_csum_diff];"
+		"r0 = 0;"
+		"exit;"
+		:
+		: __imm(bpf_get_prandom_u32),
+		  __imm(bpf_csum_diff)
+		: __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";