linux/fs/xfs/libxfs
Dave Chinner 3790a8cd8a xfs: xfs_alloc_fix_minleft can underflow near ENOSPC
Test generic/224 is failing with a corruption being detected on one
of Michael's test boxes.  Debug that Michael added is indicating
that the minleft trimming is resulting in an underflow:

.....
 before fixup:              rlen          1  args->len          0
 after xfs_alloc_fix_len  : rlen          1  args->len          1
 before goto out_nominleft: rlen          1  args->len          0
 before fixup:              rlen          1  args->len          0
 after xfs_alloc_fix_len  : rlen          1  args->len          1
 after fixup:               rlen          1  args->len          1
 before fixup:              rlen          1  args->len          0
 after xfs_alloc_fix_len  : rlen          1  args->len          1
 after fixup:               rlen 4294967295  args->len 4294967295
 XFS: Assertion failed: fs_is_ok, file: fs/xfs/libxfs/xfs_alloc.c, line: 1424

The "goto out_nominleft:" indicates that we are getting close to
ENOSPC in the AG, and a couple of allocations later we underflow
and the corruption check fires in xfs_alloc_ag_vextent_size().

The issue is that the extent length fixups comaprisons are done
with variables of xfs_extlen_t types. These are unsigned so an
underflow looks like a really big value and hence is not detected
as being smaller than the minimum length allowed for the extent.
Hence the corruption check fires as it is noticing that the returned
length is longer than the original extent length passed in.

This can be easily fixed by ensuring we do the underflow test on
signed values, the same way xfs_alloc_fix_len() prevents underflow.
So we realise in future that these casts prevent underflows from
going undetected, add comments to the code indicating this.

Reported-by: Michael L. Semon <mlsemon35@gmail.com>
Tested-by: Michael L. Semon <mlsemon35@gmail.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
2015-02-24 10:16:04 +11:00
..
xfs_alloc_btree.c xfs: merge xfs_ag.h into xfs_format.h 2014-11-28 14:25:04 +11:00
xfs_alloc_btree.h
xfs_alloc.c xfs: xfs_alloc_fix_minleft can underflow near ENOSPC 2015-02-24 10:16:04 +11:00
xfs_alloc.h xfs: merge xfs_ag.h into xfs_format.h 2014-11-28 14:25:04 +11:00
xfs_attr_leaf.c xfs: consolidate superblock logging functions 2015-01-22 09:10:31 +11:00
xfs_attr_leaf.h
xfs_attr_remote.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_attr_remote.h
xfs_attr_sf.h
xfs_attr.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_bit.h
xfs_bmap_btree.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_bmap_btree.h
xfs_bmap.c xfs: pass mp to XFS_WANT_CORRUPTED_RETURN 2015-02-23 22:39:13 +11:00
xfs_bmap.h xfs: move xfs_bmap_finish prototype 2015-01-09 10:47:14 +11:00
xfs_btree.c xfs: pass mp to XFS_WANT_CORRUPTED_RETURN 2015-02-23 22:39:13 +11:00
xfs_btree.h xfs: require 64-bit sector_t 2014-07-30 09:12:05 +10:00
xfs_cksum.h
xfs_da_btree.c Merge branch 'xfs-misc-fixes-for-3.19-2' into for-next 2014-12-04 09:46:17 +11:00
xfs_da_btree.h
xfs_da_format.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_da_format.h
xfs_dir2_block.c Merge branch 'xfs-misc-fixes-for-3.19-2' into for-next 2014-12-04 09:46:17 +11:00
xfs_dir2_data.c xfs: pass mp to XFS_WANT_CORRUPTED_RETURN 2015-02-23 22:39:13 +11:00
xfs_dir2_leaf.c Merge branch 'xfs-misc-fixes-for-3.19-2' into for-next 2014-12-04 09:46:17 +11:00
xfs_dir2_node.c Merge branch 'xfs-misc-fixes-for-3.19-2' into for-next 2014-12-04 09:46:17 +11:00
xfs_dir2_priv.h xfs: move type conversion functions to xfs_dir.h 2014-12-04 09:43:17 +11:00
xfs_dir2_sf.c Merge branch 'xfs-misc-fixes-for-3.19-2' into for-next 2014-12-04 09:46:17 +11:00
xfs_dir2.c Merge branch 'xfs-misc-fixes-for-3.19-2' into for-next 2014-12-04 09:46:17 +11:00
xfs_dir2.h xfs: move type conversion functions to xfs_dir.h 2014-12-04 09:43:17 +11:00
xfs_dquot_buf.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_format.h Merge branch 'xfs-sb-logging-rework' into for-next 2015-01-22 09:20:53 +11:00
xfs_fs.h xfs: move xfs_fs.h to libxfs 2015-01-09 10:45:13 +11:00
xfs_ialloc_btree.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_ialloc_btree.h
xfs_ialloc.c xfs: pass mp to XFS_WANT_CORRUPTED_RETURN 2015-02-23 22:39:13 +11:00
xfs_ialloc.h xfs: merge xfs_ag.h into xfs_format.h 2014-11-28 14:25:04 +11:00
xfs_inode_buf.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_inode_buf.h
xfs_inode_fork.c xfs: merge xfs_inum.h into xfs_format.h 2014-11-28 14:27:10 +11:00
xfs_inode_fork.h
xfs_log_format.h xfs: merge xfs_dinode.h into xfs_format.h 2014-11-28 14:24:06 +11:00
xfs_log_recover.h
xfs_log_rlimit.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_quota_defs.h
xfs_rtbitmap.c xfs: move most of xfs_sb.h to xfs_format.h 2014-11-28 14:27:09 +11:00
xfs_sb.c xfs: remove old and redundant comment in xfs_mount_validate_sb 2015-02-24 10:15:04 +11:00
xfs_sb.h xfs: consolidate superblock logging functions 2015-01-22 09:10:31 +11:00
xfs_shared.h xfs: consolidate superblock logging functions 2015-01-22 09:10:31 +11:00
xfs_symlink_remote.c xfs: set buf types when converting extent formats 2015-01-22 09:30:06 +11:00
xfs_trans_resv.c xfs: consolidate superblock logging functions 2015-01-22 09:10:31 +11:00
xfs_trans_resv.h xfs: consolidate superblock logging functions 2015-01-22 09:10:31 +11:00
xfs_trans_space.h
xfs_types.h xfs: move xfs_types.h to libxfs 2015-01-09 10:46:31 +11:00