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, 32 insertions, 0 deletions

diff --git a/rust/helpers/device.c b/rust/helpers/device.c
new file mode 100644
index 000000000..3be4ee590
--- /dev/null
+++ b/rust/helpers/device.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/device.h>
+
+__rust_helper int rust_helper_devm_add_action(struct device *dev,
+					      void (*action)(void *),
+					      void *data)
+{
+	return devm_add_action(dev, action, data);
+}
+
+__rust_helper int rust_helper_devm_add_action_or_reset(struct device *dev,
+						       void (*action)(void *),
+						       void *data)
+{
+	return devm_add_action_or_reset(dev, action, data);
+}
+
+__rust_helper void *rust_helper_dev_get_drvdata(const struct device *dev)
+{
+	return dev_get_drvdata(dev);
+}
+
+__rust_helper void rust_helper_dev_set_drvdata(struct device *dev, void *data)
+{
+	dev_set_drvdata(dev, data);
+}
+
+__rust_helper const char *rust_helper_dev_name(const struct device *dev)
+{
+	return dev_name(dev);
+}