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, 51 insertions, 0 deletions

diff --git a/drivers/gpio/gpiolib-shared.h b/drivers/gpio/gpiolib-shared.h
new file mode 100644
index 000000000..618756f6c
--- /dev/null
+++ b/drivers/gpio/gpiolib-shared.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __LINUX_GPIO_SHARED_H
+#define __LINUX_GPIO_SHARED_H
+
+#include <linux/mutex.h>
+
+struct gpio_device;
+struct gpio_desc;
+struct device;
+struct fwnode_handle;
+
+#if IS_ENABLED(CONFIG_GPIO_SHARED)
+
+int gpiochip_setup_shared(struct gpio_chip *gc);
+void gpio_device_teardown_shared(struct gpio_device *gdev);
+int gpio_shared_add_proxy_lookup(struct device *consumer,
+				 struct fwnode_handle *fwnode,
+				 const char *con_id, unsigned long lflags);
+
+#else
+
+static inline int gpiochip_setup_shared(struct gpio_chip *gc)
+{
+	return 0;
+}
+
+static inline void gpio_device_teardown_shared(struct gpio_device *gdev) { }
+
+static inline int gpio_shared_add_proxy_lookup(struct device *consumer,
+					       struct fwnode_handle *fwnode,
+					       const char *con_id,
+					       unsigned long lflags)
+{
+	return 0;
+}
+
+#endif /* CONFIG_GPIO_SHARED */
+
+struct gpio_shared_desc {
+	struct gpio_desc *desc;
+	unsigned long cfg;
+	unsigned int usecnt;
+	unsigned int votecnt;
+	int def_val;
+	struct mutex mutex; /* serializes all proxy operations on this descriptor */
+};
+
+struct gpio_shared_desc *devm_gpiod_shared_get(struct device *dev);
+
+#endif /* __LINUX_GPIO_SHARED_H */