memfd: pass argument of memfd_fcntl as int

The interface for fcntl expects the argument passed for the command
F_ADD_SEALS to be of type int.  The current code wrongly treats it as a
long.  In order to avoid access to undefined bits, we should explicitly
cast the argument to int.

This commit changes the signature of all the related and helper functions
so that they treat the argument as int instead of long.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Luca Vizzarro <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: Jeff Layton <[email protected]>
Cc: Chuck Lever <[email protected]>
Cc: Kevin Brodsky <[email protected]>
Cc: Vincenzo Frascino <[email protected]>
Cc: Szabolcs Nagy <[email protected]>
Cc: "Theodore Ts'o" <[email protected]>
Cc: David Laight <[email protected]>
Cc: Mark Rutland <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

include/linux/memfd.h

@@ -5,9 +5,9 @@
 #include <linux/file.h>
 
 #ifdef CONFIG_MEMFD_CREATE
-extern long memfd_fcntl(struct file *file, unsigned int cmd, unsigned long arg);
+extern long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg);
 #else
-static inline long memfd_fcntl(struct file *f, unsigned int c, unsigned long a)
+static inline long memfd_fcntl(struct file *f, unsigned int c, unsigned int a)
 {
 	return -EINVAL;
 }

mm/memfd.c

@@ -243,16 +243,12 @@ static int memfd_get_seals(struct file *file)
 	return seals ? *seals : -EINVAL;
 }
 
-long memfd_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
+long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)
 {
 	long error;
 
 	switch (cmd) {
 	case F_ADD_SEALS:
-		/* disallow upper 32bit */
-		if (arg > UINT_MAX)
-			return -EINVAL;
-
 		error = memfd_add_seals(file, arg);
 		break;
 	case F_GET_SEALS: