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xfs: fix an agbno overflow in __xfs_getfsmap_datadev

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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: Dave Chinner <david@fromorbit.com>
Fixes: 63ef7a3591 ("xfs: fix interval filtering in multi-step fsmap queries")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
This commit is contained in:
Darrick J. Wong 2023-09-11 08:39:02 -07:00
parent 0bb80ecc33
commit cfa2df68b7
1 changed files with 18 additions and 7 deletions
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25
fs/xfs/xfs_fsmap.c
View File

@ -565,6 +565,19 @@ err:
}
#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;