uaccess: Introduce ucopysize.h

The object size sanity checking macros that uaccess.h and uio.h use
have been living in thread_info.h for historical reasons. Needing to
use jump labels for these checks, however, introduces a header include
loop under certain conditions. The dependencies for the object checking
macros are very limited, but they are used by separate header files,
so introduce a new header that can be used directly by uaccess.h and
uio.h. As a result, this also means thread_info.h (which is rather large)
and be removed from those headers.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202502281153.TG2XK5SI-lkp@intel.com/
Signed-off-by: Kees Cook <kees@kernel.org>

MAINTAINERS

@@ -12586,6 +12586,7 @@ F:	Documentation/ABI/testing/sysfs-kernel-warn_count
 F:	arch/*/configs/hardening.config
 F:	include/linux/overflow.h
 F:	include/linux/randomize_kstack.h
+F:	include/linux/ucopysize.h
 F:	kernel/configs/hardening.config
 F:	lib/usercopy_kunit.c
 F:	mm/usercopy.c

include/linux/thread_info.h

@@ -217,54 +217,6 @@ static inline int arch_within_stack_frames(const void * const stack,
 }
 #endif
 
-#ifdef CONFIG_HARDENED_USERCOPY
-extern void __check_object_size(const void *ptr, unsigned long n,
-					bool to_user);
-
-static __always_inline void check_object_size(const void *ptr, unsigned long n,
-					      bool to_user)
-{
-	if (!__builtin_constant_p(n))
-		__check_object_size(ptr, n, to_user);
-}
-#else
-static inline void check_object_size(const void *ptr, unsigned long n,
-				     bool to_user)
-{ }
-#endif /* CONFIG_HARDENED_USERCOPY */
-
-extern void __compiletime_error("copy source size is too small")
-__bad_copy_from(void);
-extern void __compiletime_error("copy destination size is too small")
-__bad_copy_to(void);
-
-void __copy_overflow(int size, unsigned long count);
-
-static inline void copy_overflow(int size, unsigned long count)
-{
-	if (IS_ENABLED(CONFIG_BUG))
-		__copy_overflow(size, count);
-}
-
-static __always_inline __must_check bool
-check_copy_size(const void *addr, size_t bytes, bool is_source)
-{
-	int sz = __builtin_object_size(addr, 0);
-	if (unlikely(sz >= 0 && sz < bytes)) {
-		if (!__builtin_constant_p(bytes))
-			copy_overflow(sz, bytes);
-		else if (is_source)
-			__bad_copy_from();
-		else
-			__bad_copy_to();
-		return false;
-	}
-	if (WARN_ON_ONCE(bytes > INT_MAX))
-		return false;
-	check_object_size(addr, bytes, is_source);
-	return true;
-}
-
 #ifndef arch_setup_new_exec
 static inline void arch_setup_new_exec(void) { }
 #endif

include/linux/uaccess.h

@@ -7,7 +7,7 @@
 #include <linux/minmax.h>
 #include <linux/nospec.h>
 #include <linux/sched.h>
-#include <linux/thread_info.h>
+#include <linux/ucopysize.h>
 
 #include <asm/uaccess.h>
 

include/linux/ucopysize.h

@@ -0,0 +1,56 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Perform sanity checking for object sizes for uaccess.h and uio.h. */
+#ifndef __LINUX_UCOPYSIZE_H__
+#define __LINUX_UCOPYSIZE_H__
+
+#include <linux/bug.h>
+
+#ifdef CONFIG_HARDENED_USERCOPY
+extern void __check_object_size(const void *ptr, unsigned long n,
+					bool to_user);
+
+static __always_inline void check_object_size(const void *ptr, unsigned long n,
+					      bool to_user)
+{
+	if (!__builtin_constant_p(n))
+		__check_object_size(ptr, n, to_user);
+}
+#else
+static inline void check_object_size(const void *ptr, unsigned long n,
+				     bool to_user)
+{ }
+#endif /* CONFIG_HARDENED_USERCOPY */
+
+extern void __compiletime_error("copy source size is too small")
+__bad_copy_from(void);
+extern void __compiletime_error("copy destination size is too small")
+__bad_copy_to(void);
+
+void __copy_overflow(int size, unsigned long count);
+
+static inline void copy_overflow(int size, unsigned long count)
+{
+	if (IS_ENABLED(CONFIG_BUG))
+		__copy_overflow(size, count);
+}
+
+static __always_inline __must_check bool
+check_copy_size(const void *addr, size_t bytes, bool is_source)
+{
+	int sz = __builtin_object_size(addr, 0);
+	if (unlikely(sz >= 0 && sz < bytes)) {
+		if (!__builtin_constant_p(bytes))
+			copy_overflow(sz, bytes);
+		else if (is_source)
+			__bad_copy_from();
+		else
+			__bad_copy_to();
+		return false;
+	}
+	if (WARN_ON_ONCE(bytes > INT_MAX))
+		return false;
+	check_object_size(addr, bytes, is_source);
+	return true;
+}
+
+#endif /* __LINUX_UCOPYSIZE_H__ */

include/linux/uio.h

@@ -6,8 +6,8 @@
 #define __LINUX_UIO_H
 
 #include <linux/kernel.h>
-#include <linux/thread_info.h>
 #include <linux/mm_types.h>
+#include <linux/ucopysize.h>
 #include <uapi/linux/uio.h>
 
 struct page;

mm/usercopy.c

@@ -17,7 +17,7 @@
 #include <linux/sched.h>
 #include <linux/sched/task.h>
 #include <linux/sched/task_stack.h>
-#include <linux/thread_info.h>
+#include <linux/ucopysize.h>
 #include <linux/vmalloc.h>
 #include <linux/atomic.h>
 #include <linux/jump_label.h>