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, 37 insertions, 0 deletions

diff --git a/fs/sysctls.c b/fs/sysctls.c
new file mode 100644
index 000000000..ad429dffe
--- /dev/null
+++ b/fs/sysctls.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * /proc/sys/fs shared sysctls
+ *
+ * These sysctls are shared between different filesystems.
+ */
+#include <linux/init.h>
+#include <linux/sysctl.h>
+
+static const struct ctl_table fs_shared_sysctls[] = {
+	{
+		.procname	= "overflowuid",
+		.data		= &fs_overflowuid,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_MAXOLDUID,
+	},
+	{
+		.procname	= "overflowgid",
+		.data		= &fs_overflowgid,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_MAXOLDUID,
+	},
+};
+
+static int __init init_fs_sysctls(void)
+{
+	register_sysctl_init("fs", fs_shared_sysctls);
+	return 0;
+}
+
+early_initcall(init_fs_sysctls);