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From:   bugzilla-daemon@bugzilla.kernel.org
To:     linux-ext4@vger.kernel.org
Subject: [Bug 213357] New: chattr +e writes invalid checksum to extent block
Date:   Mon, 07 Jun 2021 16:03:57 +0000
Message-ID: <bug-213357-13602@https.bugzilla.kernel.org/>
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https://bugzilla.kernel.org/show_bug.cgi?id=3D213357

            Bug ID: 213357
           Summary: chattr +e writes invalid checksum to extent block
           Product: File System
           Version: 2.5
    Kernel Version: 5.13.0-rc4
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: ext4
          Assignee: fs_ext4@kernel-bugs.osdl.org
          Reporter: jeroen@wolffelaar.nl
        Regression: No

Created attachment 297207
  --> https://bugzilla.kernel.org/attachment.cgi?id=3D297207&action=3Dedit
Reproduction script

Overview:

Converting a file previously using (ext2/3) blocklists to ext4 extents using
chattr +e makes the kernel write an invalid checksum to the extent block (if
one needs to be written because of the metadata_csum feature & there being =
more
than 4 extents). Because of inode caching, this won't be obvious until the
inode has has been evicted from the cache, or the filesystem is remounted. =
The
checksum errors are trivially correctable using e2fsck.

Reproduction:

In short:

* Create a large enough file on an ext3 filesystem to have it 5+ discontinu=
ous
ranges of blocks
* Add 'extent' and 'metadata_csum' feature to the filesystem
* chattr +e the file
* Reload the filesystem/clear inode cache

See repro.sh for full steps.

Observe:

* Reading the file gives I/O errors (EXT4-fs error: ext4_find_extent:885: i=
node
#12: comm cat: pblk 17591 bad header/extent: extent tree corrupted - magic
f30a, entries 6, max 340(340), depth 0(0))
* e2fsck reports checksum mismatch (ext2fs_block_iterate3: Extent block
checksum does not match extent block)

Reproduction:

Besides the system where I originally found the bug, I reproduced it with 3
Debian versions (Stretch, Buster, Bullseye rc1), and additionally Bullseye =
with
vanilla 5.13.0-rc4 kernel built from kernel.org source tarball: so, kernel
versions spanning 4.9 to 5.13.

The reproduction script is destructive to the provided device.

--=20
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