stackleak: let stack_erasing_sysctl take a kernel pointer buffer

Commit 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler")
changed ctl_table.proc_handler to take a kernel pointer. Adjust the
signature of stack_erasing_sysctl to match ctl_table.proc_handler which
fixes the following sparse warning:

kernel/stackleak.c:31:50: warning: incorrect type in argument 3 (different address spaces)
kernel/stackleak.c:31:50: expected void *
kernel/stackleak.c:31:50: got void [noderef] __user *buffer

Fixes: 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler")
Signed-off-by: Tobias Klauser <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: Al Viro <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/stackleak.h

···
 
 #ifdef CONFIG_STACKLEAK_RUNTIME_DISABLE
 int stack_erasing_sysctl(struct ctl_table *table, int write,
-			void __user *buffer, size_t *lenp, loff_t *ppos);
+			void *buffer, size_t *lenp, loff_t *ppos);
 #endif
 
 #else /* !CONFIG_GCC_PLUGIN_STACKLEAK */

kernel/stackleak.c

···
 static DEFINE_STATIC_KEY_FALSE(stack_erasing_bypass);
 
 int stack_erasing_sysctl(struct ctl_table *table, int write,
-			void __user *buffer, size_t *lenp, loff_t *ppos)
+			void *buffer, size_t *lenp, loff_t *ppos)
 {
 	int ret = 0;
 	int state = !static_branch_unlikely(&stack_erasing_bypass);