Commit cfa2df68 authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

xfs: fix an agbno overflow in __xfs_getfsmap_datadev 



Dave Chinner reported that xfs/273 fails if the AG size happens to be an
exact power of two.  I traced this to an agbno integer overflow when the
current GETFSMAP call is a continuation of a previous GETFSMAP call, and
the last record returned was non-shareable space at the end of an AG.

__xfs_getfsmap_datadev sets up a data device query by converting the
incoming fmr_physical into an xfs_fsblock_t and cracking it into an agno
and agbno pair.  In the (failing) case of where fmr_blockcount of the
low key is nonzero and the record was for a non-shareable extent, it
will add fmr_blockcount to start_fsb and info->low.rm_startblock.

If the low key was actually the last record for that AG, then this
addition causes info->low.rm_startblock to point beyond EOAG.  When the
rmapbt range query starts, it'll return an empty set, and fsmap moves on
to the next AG.

Or so I thought.  Remember how we added to start_fsb?

If agsize < 1<<agblklog, start_fsb points to the same AG as the original
fmr_physical from the low key.  We run the rmapbt query, which returns
nothing, so getfsmap zeroes info->low and moves on to the next AG.

If agsize == 1<<agblklog, start_fsb now points to the next AG.  We run
the rmapbt query on the next AG with the excessively large
rm_startblock.  If this next AG is actually the last AG, we'll set
info->high to EOFS (which is now has a lower rm_startblock than
info->low), and the ranged btree query code will return -EINVAL.  If
it's not the last AG, we ignore all records for the intermediate AGs.

Oops.

Fix this by decoding start_fsb into agno and agbno only after making
adjustments to start_fsb.  This means that info->low.rm_startblock will
always be set to a valid agbno, and we always start the rmapbt iteration
in the correct AG.

While we're at it, fix the predicate for determining if an fsmap record
represents non-shareable space to include file data on pre-reflink
filesystems.

Reported-by: default avatarDave Chinner <david@fromorbit.com>
Fixes: 63ef7a35 ("xfs: fix interval filtering in multi-step fsmap queries")
Signed-off-by: default avatarDarrick J. Wong <djwong@kernel.org>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
parent 0bb80ecc

fs/xfs/xfs_fsmap.c

+18 −7
Original line number Diff line number Diff line
@@ -565,6 +565,19 @@ xfs_getfsmap_rtdev_rtbitmap( 
}

#endif /* CONFIG_XFS_RT */



static inline bool

rmap_not_shareable(struct xfs_mount *mp, const struct xfs_rmap_irec *r)

{

	if (!xfs_has_reflink(mp))

		return true;

	if (XFS_RMAP_NON_INODE_OWNER(r->rm_owner))

		return true;

	if (r->rm_flags & (XFS_RMAP_ATTR_FORK | XFS_RMAP_BMBT_BLOCK |

			   XFS_RMAP_UNWRITTEN))

		return true;

	return false;

}



/* Execute a getfsmap query against the regular data device. */

STATIC int

__xfs_getfsmap_datadev(
@@ -598,7 +611,6 @@ __xfs_getfsmap_datadev( 
	 * low to the fsmap low key and max out the high key to the end

	 * of the AG.

	 */

	info->low.rm_startblock = XFS_FSB_TO_AGBNO(mp, start_fsb);

	info->low.rm_offset = XFS_BB_TO_FSBT(mp, keys[0].fmr_offset);

	error = xfs_fsmap_owner_to_rmap(&info->low, &keys[0]);

	if (error)
@@ -608,12 +620,9 @@ __xfs_getfsmap_datadev( 


	/* Adjust the low key if we are continuing from where we left off. */

	if (info->low.rm_blockcount == 0) {

		/* empty */

	} else if (XFS_RMAP_NON_INODE_OWNER(info->low.rm_owner) ||

		   (info->low.rm_flags & (XFS_RMAP_ATTR_FORK |

					  XFS_RMAP_BMBT_BLOCK |

					  XFS_RMAP_UNWRITTEN))) {

		info->low.rm_startblock += info->low.rm_blockcount;

		/* No previous record from which to continue */

	} else if (rmap_not_shareable(mp, &info->low)) {

		/* Last record seen was an unshareable extent */

		info->low.rm_owner = 0;

		info->low.rm_offset = 0;
@@ -621,8 +630,10 @@ __xfs_getfsmap_datadev( 
		if (XFS_FSB_TO_DADDR(mp, start_fsb) >= eofs)

			return 0;

	} else {

		/* Last record seen was a shareable file data extent */

		info->low.rm_offset += info->low.rm_blockcount;

	}

	info->low.rm_startblock = XFS_FSB_TO_AGBNO(mp, start_fsb);



	info->high.rm_startblock = -1U;

	info->high.rm_owner = ULLONG_MAX;