fs: add missing compat_ptr handling for FS_IOC_RESVSP ioctl

For FS_IOC_RESVSP and FS_IOC_RESVSP64 compat_sys_ioctl() uses its
arg argument as a pointer to userspace. However it is missing a
a call to compat_ptr() which will do a proper pointer conversion.

This was introduced with 3e63cbb1 "fs: Add new pre-allocation ioctls
to vfs for compatibility with legacy xfs ioctls".

Signed-off-by: Heiko Carstens <[e-mail]>
Cc: Ankit Jain <[e-mail]>
Acked-by: Christoph Hellwig <[e-mail]>
Cc: Al Viro <[e-mail]>
Acked-by: Arnd Bergmann <[e-mail]>
Acked-by: David S. Miller <[e-mail]>
Cc: <[e-mail]> [2.6.31.x]
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/compat_ioctl.c

···
 /* just account for different alignment */
 static int compat_ioctl_preallocate(struct file *file, unsigned long arg)
 {
-	struct space_resv_32	__user *p32 = (void __user *)arg;
+	struct space_resv_32	__user *p32 = compat_ptr(arg);
 	struct space_resv	__user *p = compat_alloc_user_space(sizeof(*p));
 
 	if (copy_in_user(&p->l_type,	&p32->l_type,	sizeof(s16)) ||
···
 #else
 	case FS_IOC_RESVSP:
 	case FS_IOC_RESVSP64:
-		error = ioctl_preallocate(filp, (void __user *)arg);
+		error = ioctl_preallocate(filp, compat_ptr(arg));
 		goto out_fput;
 #endif