xfs: kill the XFS_IOC_{ALLOC,FREE}SP* ioctls

According to the glibc compat header for Irix 4, these ioctls originated
in April 1991 as a (somewhat clunky) way to preallocate space at the end
of a file on an EFS filesystem. XFS, which was released in Irix 5.3 in
December 1993, picked up these ioctls to maintain compatibility and they
were ported to Linux in the early 2000s.

Recently it was pointed out to me they still lurk in the kernel, even
though the Linux fallocate syscall supplanted the functionality a long
time ago. fstests doesn't seem to include any real functional or stress
tests for these ioctls, which means that the code quality is ... very
questionable. Most notably, it was a stale disk block exposure vector
for 21 years and nobody noticed or complained. As mature programmers
say, "If you're not testing it, it's broken."

Given all that, let's withdraw these ioctls from the XFS userspace API.
Normally we'd set a long deprecation process, but I estimate that there
aren't any real users, so let's trigger a warning in dmesg and return
-ENOTTY.

See: CVE-2021-4155

Augments: 983d8e60f508 ("xfs: map unwritten blocks in XFS_IOC_{ALLOC,FREE}SP just like fallocate")
Signed-off-by: Darrick J. Wong <[e-mail]>
Reviewed-by: Eric Sandeen <[e-mail]>
Reviewed-by: Dave Chinner <[e-mail]>

fs/xfs/xfs_bmap_util.c

···
 xfs_alloc_file_space(
 	struct xfs_inode	*ip,
 	xfs_off_t		offset,
-	xfs_off_t		len,
-	int			alloc_type)
+	xfs_off_t		len)
 {
 	xfs_mount_t		*mp = ip->i_mount;
 	xfs_off_t		count;
···
 			goto error;
 
 		error = xfs_bmapi_write(tp, ip, startoffset_fsb,
-					allocatesize_fsb, alloc_type, 0, imapp,
-					&nimaps);
+				allocatesize_fsb, XFS_BMAPI_PREALLOC, 0, imapp,
+				&nimaps);
 		if (error)
 			goto error;
 

fs/xfs/xfs_bmap_util.h

···
 
 /* preallocation and hole punch interface */
 int	xfs_alloc_file_space(struct xfs_inode *ip, xfs_off_t offset,
-			     xfs_off_t len, int alloc_type);
+			     xfs_off_t len);
 int	xfs_free_file_space(struct xfs_inode *ip, xfs_off_t offset,
 			    xfs_off_t len);
 int	xfs_collapse_file_space(struct xfs_inode *, xfs_off_t offset,

fs/xfs/xfs_file.c

···
 		}
 
 		if (!xfs_is_always_cow_inode(ip)) {
-			error = xfs_alloc_file_space(ip, offset, len,
-						     XFS_BMAPI_PREALLOC);
+			error = xfs_alloc_file_space(ip, offset, len);
 			if (error)
 				goto out_unlock;
 		}

fs/xfs/xfs_ioctl.c

···
 	return error;
 }
 
-int
-xfs_ioc_space(
-	struct file		*filp,
-	xfs_flock64_t		*bf)
-{
-	struct inode		*inode = file_inode(filp);
-	struct xfs_inode	*ip = XFS_I(inode);
-	struct iattr		iattr;
-	enum xfs_prealloc_flags	flags = XFS_PREALLOC_CLEAR;
-	uint			iolock = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
-	int			error;
-
-	if (inode->i_flags & (S_IMMUTABLE|S_APPEND))
-		return -EPERM;
-
-	if (!(filp->f_mode & FMODE_WRITE))
-		return -EBADF;
-
-	if (!S_ISREG(inode->i_mode))
-		return -EINVAL;
-
-	if (xfs_is_always_cow_inode(ip))
-		return -EOPNOTSUPP;
-
-	if (filp->f_flags & O_DSYNC)
-		flags |= XFS_PREALLOC_SYNC;
-	if (filp->f_mode & FMODE_NOCMTIME)
-		flags |= XFS_PREALLOC_INVISIBLE;
-
-	error = mnt_want_write_file(filp);
-	if (error)
-		return error;
-
-	xfs_ilock(ip, iolock);
-	error = xfs_break_layouts(inode, &iolock, BREAK_UNMAP);
-	if (error)
-		goto out_unlock;
-	inode_dio_wait(inode);
-
-	switch (bf->l_whence) {
-	case 0: /*SEEK_SET*/
-		break;
-	case 1: /*SEEK_CUR*/
-		bf->l_start += filp->f_pos;
-		break;
-	case 2: /*SEEK_END*/
-		bf->l_start += XFS_ISIZE(ip);
-		break;
-	default:
-		error = -EINVAL;
-		goto out_unlock;
-	}
-
-	if (bf->l_start < 0 || bf->l_start > inode->i_sb->s_maxbytes) {
-		error = -EINVAL;
-		goto out_unlock;
-	}
-
-	if (bf->l_start > XFS_ISIZE(ip)) {
-		error = xfs_alloc_file_space(ip, XFS_ISIZE(ip),
-				bf->l_start - XFS_ISIZE(ip), 0);
-		if (error)
-			goto out_unlock;
-	}
-
-	iattr.ia_valid = ATTR_SIZE;
-	iattr.ia_size = bf->l_start;
-	error = xfs_vn_setattr_size(file_mnt_user_ns(filp), file_dentry(filp),
-				    &iattr);
-	if (error)
-		goto out_unlock;
-
-	error = xfs_update_prealloc_flags(ip, flags);
-
-out_unlock:
-	xfs_iunlock(ip, iolock);
-	mnt_drop_write_file(filp);
-	return error;
-}
-
 /* Return 0 on success or positive error */
 int
 xfs_fsbulkstat_one_fmt(
···
 	case XFS_IOC_ALLOCSP:
 	case XFS_IOC_FREESP:
 	case XFS_IOC_ALLOCSP64:
-	case XFS_IOC_FREESP64: {
-		xfs_flock64_t		bf;
-
-		if (copy_from_user(&bf, arg, sizeof(bf)))
-			return -EFAULT;
-		return xfs_ioc_space(filp, &bf);
-	}
+	case XFS_IOC_FREESP64:
+		xfs_warn_once(mp,
+	"%s should use fallocate; XFS_IOC_{ALLOC,FREE}SP ioctl unsupported",
+				current->comm);
+		return -ENOTTY;
 	case XFS_IOC_DIOINFO: {
 		struct xfs_buftarg	*target = xfs_inode_buftarg(ip);
 		struct dioattr		da;

fs/xfs/xfs_ioctl.h

···
 struct xfs_ibulk;
 struct xfs_inogrp;
 
-
-extern int
-xfs_ioc_space(
-	struct file		*filp,
-	xfs_flock64_t		*bf);
-
 int
 xfs_ioc_swapext(
 	xfs_swapext_t	*sxp);

fs/xfs/xfs_ioctl32.c

···
 
 #ifdef BROKEN_X86_ALIGNMENT
 STATIC int
-xfs_compat_flock64_copyin(
-	xfs_flock64_t		*bf,
-	compat_xfs_flock64_t	__user *arg32)
-{
-	if (get_user(bf->l_type,	&arg32->l_type) ||
-	    get_user(bf->l_whence,	&arg32->l_whence) ||
-	    get_user(bf->l_start,	&arg32->l_start) ||
-	    get_user(bf->l_len,		&arg32->l_len) ||
-	    get_user(bf->l_sysid,	&arg32->l_sysid) ||
-	    get_user(bf->l_pid,		&arg32->l_pid) ||
-	    copy_from_user(bf->l_pad,	&arg32->l_pad,	4*sizeof(u32)))
-		return -EFAULT;
-	return 0;
-}
-
-STATIC int
 xfs_compat_ioc_fsgeometry_v1(
 	struct xfs_mount	  *mp,
 	compat_xfs_fsop_geom_v1_t __user *arg32)
···
 
 	switch (cmd) {
 #if defined(BROKEN_X86_ALIGNMENT)
-	case XFS_IOC_ALLOCSP_32:
-	case XFS_IOC_FREESP_32:
-	case XFS_IOC_ALLOCSP64_32:
-	case XFS_IOC_FREESP64_32: {
-		struct xfs_flock64	bf;
-
-		if (xfs_compat_flock64_copyin(&bf, arg))
-			return -EFAULT;
-		cmd = _NATIVE_IOC(cmd, struct xfs_flock64);
-		return xfs_ioc_space(filp, &bf);
-	}
 	case XFS_IOC_FSGEOMETRY_V1_32:
 		return xfs_compat_ioc_fsgeometry_v1(ip->i_mount, arg);
 	case XFS_IOC_FSGROWFSDATA_32: {