xfs: refactor file range validation

Refactor all the open-coded validation of file block ranges into a
single helper, and teach the bmap scrubber to check the ranges.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_bmap.c

@@ -6227,7 +6227,7 @@ xfs_bmap_validate_extent(
 {
 	struct xfs_mount	*mp = ip->i_mount;
 
-	if (irec->br_startoff + irec->br_blockcount <= irec->br_startoff)
+	if (!xfs_verify_fileext(mp, irec->br_startoff, irec->br_blockcount))
 		return __this_address;
 
 	if (XFS_IS_REALTIME_INODE(ip) && whichfork == XFS_DATA_FORK) {

fs/xfs/libxfs/xfs_types.c

@@ -258,3 +258,28 @@ xfs_verify_dablk(
 
 	return dabno <= max_dablk;
 }
+
+/* Check that a file block offset does not exceed the maximum. */
+bool
+xfs_verify_fileoff(
+	struct xfs_mount	*mp,
+	xfs_fileoff_t		off)
+{
+	return off <= XFS_MAX_FILEOFF;
+}
+
+/* Check that a range of file block offsets do not exceed the maximum. */
+bool
+xfs_verify_fileext(
+	struct xfs_mount	*mp,
+	xfs_fileoff_t		off,
+	xfs_fileoff_t		len)
+{
+	if (off + len <= off)
+		return false;
+
+	if (!xfs_verify_fileoff(mp, off))
+		return false;
+
+	return xfs_verify_fileoff(mp, off + len - 1);
+}

fs/xfs/libxfs/xfs_types.h

@@ -203,5 +203,8 @@ bool xfs_verify_icount(struct xfs_mount *mp, unsigned long long icount);
 bool xfs_verify_dablk(struct xfs_mount *mp, xfs_fileoff_t off);
 void xfs_icount_range(struct xfs_mount *mp, unsigned long long *min,
 		unsigned long long *max);
+bool xfs_verify_fileoff(struct xfs_mount *mp, xfs_fileoff_t off);
+bool xfs_verify_fileext(struct xfs_mount *mp, xfs_fileoff_t off,
+		xfs_fileoff_t len);
 
 #endif	/* __XFS_TYPES_H__ */

fs/xfs/scrub/bmap.c

@@ -329,6 +329,10 @@ xchk_bmap_iextent(
 		xchk_fblock_set_corrupt(info->sc, info->whichfork,
 				irec->br_startoff);
 
+	if (!xfs_verify_fileext(mp, irec->br_startoff, irec->br_blockcount))
+		xchk_fblock_set_corrupt(info->sc, info->whichfork,
+				irec->br_startoff);
+
 	xchk_bmap_dirattr_extent(ip, info, irec);
 
 	/* There should never be a "hole" extent in either extent list. */

fs/xfs/xfs_bmap_item.c

@@ -445,7 +445,7 @@ xfs_bui_validate(
 	if (!xfs_verify_ino(mp, bmap->me_owner))
 		return false;
 
-	if (bmap->me_startoff + bmap->me_len <= bmap->me_startoff)
+	if (!xfs_verify_fileext(mp, bmap->me_startoff, bmap->me_len))
 		return false;
 
 	return xfs_verify_fsbext(mp, bmap->me_startblock, bmap->me_len);

fs/xfs/xfs_inode.c

@@ -1521,7 +1521,7 @@ xfs_itruncate_extents_flags(
 	 * the page cache can't scale that far.
 	 */
 	first_unmap_block = XFS_B_TO_FSB(mp, (xfs_ufsize_t)new_size);
-	if (first_unmap_block >= XFS_MAX_FILEOFF) {
+	if (!xfs_verify_fileoff(mp, first_unmap_block)) {
 		WARN_ON_ONCE(first_unmap_block > XFS_MAX_FILEOFF);
 		return 0;
 	}

fs/xfs/xfs_rmap_item.c

@@ -490,7 +490,7 @@ xfs_rui_validate_map(
 	    !xfs_verify_ino(mp, rmap->me_owner))
 		return false;
 
-	if (rmap->me_startoff + rmap->me_len <= rmap->me_startoff)
+	if (!xfs_verify_fileext(mp, rmap->me_startoff, rmap->me_len))
 		return false;
 
 	return xfs_verify_fsbext(mp, rmap->me_startblock, rmap->me_len);

fs/xfs/xfs_super.c

@@ -1517,7 +1517,7 @@ xfs_fc_fill_super(
 	 * Avoid integer overflow by comparing the maximum bmbt offset to the
 	 * maximum pagecache offset in units of fs blocks.
 	 */
-	if (XFS_B_TO_FSBT(mp, MAX_LFS_FILESIZE) > XFS_MAX_FILEOFF) {
+	if (!xfs_verify_fileoff(mp, XFS_B_TO_FSBT(mp, MAX_LFS_FILESIZE))) {
 		xfs_warn(mp,
 "MAX_LFS_FILESIZE block offset (%llu) exceeds extent map maximum (%llu)!",
 			 XFS_B_TO_FSBT(mp, MAX_LFS_FILESIZE),