[LU-16569] chattr makes file unavailable

• Status: Open
• Project: Lustre
• Affects Version/s: Lustre 2.16.0
• Type: Bug
• Priority: Major
• Reporter: Alexander Boyko
• Assignee: Sebastien Buisson
• Resolution: Unresolved
• Severity: 3

Description

Here is the problem, Lustre does not filter supported attributes and as a result file became unaccessible.

$touch /mnt/lustre/f2
$lsattr /mnt/lustre/f2
---------------------- /mnt/lustre/f2
$chattr +aAcCdDeFijmPsStTux /mnt/lustre/f2
$lsattr /mnt/lustre/f2
lsattr: No data available While reading flags on /mnt/lustre/f2
$cat /mnt/lustre/f2
cat: /mnt/lustre/f2: No data available
$statx /mnt/lustre/f2
  File: /mnt/lustre/f2
  Size: 0         	Blocks: 0          IO Block: 4194304 regular empty file
Device: 2c54f966h/743766374d	Inode: 144115205272502274  Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Context: unconfined_u:object_r:unlabeled_t:s0
Access: 2023-02-16 18:08:06.000000000 -0500
Modify: 2023-02-16 18:08:06.000000000 -0500
Change: 2023-02-16 18:08:06.000000000 -0500
 Birth: 2023-02-16 18:08:06.000000000 -0500

Comments

[Andreas Dilger]

This definitely looks like it could screw up encrypted files:

# for F in a A c C d D e F i j m P s S t T u x; do
     touch /mnt/testfs/dir_attr/f-$F
     chattr +$F /mnt/testfs/dir_attr/f-$F
done

# ls -l /mnt/testfs/dir_attr
total 0
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-a
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-A
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-c
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-C
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-d
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-D
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-e
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-F
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-i
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-j
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-m
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-P
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-s
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-S
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-t
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-T
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-u
0 -rw-r--r--. 1 root 0 Feb 17 18:40 f-x

# lsattr /mnt/testfs/dir_attr
---------------------- /mnt/testfs/dir_attr/f-F
---------------------- /mnt/testfs/dir_attr/f-c
---------------------- /mnt/testfs/dir_attr/f-d
---------------------- /mnt/testfs/dir_attr/f-D
---------------------- /mnt/testfs/dir_attr/f-m
-------A-------------- /mnt/testfs/dir_attr/f-A
lsattr: Required key not available While reading flags on /mnt/testfs/dir_attr/f-C
---------------------- /mnt/testfs/dir_attr/f-s
--S------------------- /mnt/testfs/dir_attr/f-S
---------------------- /mnt/testfs/dir_attr/f-T
---------------------- /mnt/testfs/dir_attr/f-x
---------------------- /mnt/testfs/dir_attr/f-u
-------------------P-- /mnt/testfs/dir_attr/f-P
-----a---------------- /mnt/testfs/dir_attr/f-a
----i----------------- /mnt/testfs/dir_attr/f-i
---------------------- /mnt/testfs/dir_attr/f-t
---------------------- /mnt/testfs/dir_attr/f-e
---------------------- /mnt/testfs/dir_attr/f-j

While I'm not sure the clients should filter the flags (since they may not know which ones the servers support), definitely the MDS should filter the unknown/unsupported flags (or whitelist only known flags). I think there is a flag whitelist in newer ext4 code, not sure what version that appeared in, but we might also bypass those checks in osd-ldiskfs.

[Sebastien Buisson]

lsattr: Required key not available While reading flags on /mnt/testfs/dir_attr/f-C

I am not even sure why it complains about a 'key' on the file f-C, as it just has a COW-related flag:

C      A file with the 'C' attribute set will not be subject to
              copy-on-write updates.  This flag is only supported on
              file systems which perform copy-on-write.  (Note: For
              btrfs, the 'C' flag should be set on new or empty files.
              If it is set on a file which already has data blocks, it
              is undefined when the blocks assigned to the file will be
              fully stable.  If the 'C' flag is set on a directory, it
              will have no effect on the directory, but new files
              created in that directory will have the No_COW attribute
              set. If the 'C' flag is set, then the 'c' flag cannot be
              set.)