fsverity: use register_sysctl_init() to avoid kmemleak warning

Since the fsverity sysctl registration runs as a builtin initcall, there
is no corresponding sysctl deregistration and the resulting struct
ctl_table_header is not used. This can cause a kmemleak warning just
after the system boots up. (A pointer to the ctl_table_header is stored
in the fsverity_sysctl_header static variable, which kmemleak should
detect; however, the compiler can optimize out that variable.) Avoid
the kmemleak warning by using register_sysctl_init() which is intended
for use by builtin initcalls and uses kmemleak_not_leak().

Reported-by: Yi Zhang <[e-mail]>
Closes: https://lore.kernel.org/r/[e-mail]
Cc: [e-mail]
Reviewed-by: Joel Granados <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Eric Biggers <[e-mail]>

fs/verity/init.c

···
 #include <linux/ratelimit.h>
 
 #ifdef CONFIG_SYSCTL
-static struct ctl_table_header *fsverity_sysctl_header;
-
 static struct ctl_table fsverity_sysctl_table[] = {
 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
 	{
···
 
 static void __init fsverity_init_sysctl(void)
 {
-	fsverity_sysctl_header = register_sysctl("fs/verity",
-						 fsverity_sysctl_table);
-	if (!fsverity_sysctl_header)
-		panic("fsverity sysctl registration failed");
+	register_sysctl_init("fs/verity", fsverity_sysctl_table);
 }
 #else /* CONFIG_SYSCTL */
 static inline void fsverity_init_sysctl(void)