bpf: mark a NULL kfunc argument precisegrafted

check_kfunc_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 30 insertions, 0 deletions

diff --git a/arch/mips/generic/proc.c b/arch/mips/generic/proc.c
new file mode 100644
index 000000000..cce2fde21
--- /dev/null
+++ b/arch/mips/generic/proc.c
@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2016 Imagination Technologies
+ * Author: Paul Burton <paul.burton@mips.com>
+ */
+
+#include <linux/of.h>
+
+#include <asm/bootinfo.h>
+
+char *system_type;
+
+const char *get_system_type(void)
+{
+	const char *str;
+	int err;
+
+	if (system_type)
+		return system_type;
+
+	err = of_property_read_string(of_root, "model", &str);
+	if (!err)
+		return str;
+
+	err = of_property_read_string_index(of_root, "compatible", 0, &str);
+	if (!err)
+		return str;
+
+	return "Unknown";
+}