[Bug 206879] New: "extent tree corrupted" after several syscalls involving EXT4_IOC_SWAP_BOOT on a sparse file

[Bug 206879] New: "extent tree corrupted" after several syscalls involving EXT4_IOC_SWAP_BOOT on a sparse file

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=206879

            Bug ID: 206879
           Summary: "extent tree corrupted" after several syscalls
                    involving EXT4_IOC_SWAP_BOOT on a sparse file
           Product: File System
           Version: 2.5
    Kernel Version: tytso/ext4/dev (dce8e2371)
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: ext4
          Assignee: fs_ext4@kernel-bugs.osdl.org
          Reporter: anatoly.trosinenko@gmail.com
        Regression: No

Created attachment 287969
  --> https://bugzilla.kernel.org/attachment.cgi?id=287969&action=edit
Reproducer

Hello,

By fuzzing, I have found an "extent tree corrupted" message after invoking
several syscalls on a clean ext4 file system image. Some of these are quite
special ioctls probably mis-used by my fuzzer, still I report this just in
case.

How to reproduce (with kvm-xfstests):

1) Checkout tytso/ext4 branch dev (commit dce8e2371)
2) cp /path/to/fstests/kernel-configs/x86_64-config-5.4 .config
3) make olddefconfig
4) make
5) Compile the attached reproducer:

   gcc ext4-test.c -o /tmp/kvm-xfstests-USER/repro -static

   In my case, the kernel was built for amd64, so reproducer is for amd64, too.
With `-m32`, I get a ENOTTY error on EXT4_IOC_SWAP_BOOT
6) Run `./kvm-xfstests shell`
7) Inside the shell:
   mke2fs -t ext4 test.img 1024M
   mount test.img /mnt
   /vtmp/repro /mnt/123 /mnt/abc
8) Observe in dmesg:
   [  114.760535] EXT4-fs error (device loop0): ext4_ext_precache:579: inode
#12: comm repro: pblk 32897 bad header/extent: extent tree corrupted - magic
f30a, entries 5, max 340(340), depth 0(0)

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