[Bug 203861] New: Division by zero error in fsck.f2fs when fixing a corrupted image

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=203861

            Bug ID: 203861
           Summary: Division by zero error in fsck.f2fs when fixing a
                    corrupted image
           Product: File System
           Version: 2.5
    Kernel Version: v4.18
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: f2fs
          Assignee: filesystem_f2fs@kernel-bugs.kernel.org
          Reporter: seulbae@gatech.edu
        Regression: No

Created attachment 283179
  --> https://bugzilla.kernel.org/attachment.cgi?id=283179&action=edit
Corrupted f2fs image (compressed)

[Overview]
fsck.f2fs of f2fs-tools (master at commit 54244dcafd) triggers a division by
zero error while fixing a corrupted image, in which segs->secs_per_zone is set
to 0.

[Reproduction]
Download and uncompress the attached image.
Run fsck.f2fs against the downloaded image:
$ cd path/to/f2fs-tools/
$ ./fsck/fsck.f2fs -d 0 -f /tmp/f2fs.img
Info: Force to fix corruption
Info: Segments per section = 1
Info: Sections per zone = 1
Info: sector size = 512
Info: total sectors = 131072 (64 MB)
Info: MKFS version
  "Linux version 4.13.0-45-generic (buildd@lgw01-amd64-011) (gcc version 5.4.0
20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.9)) #50~16.04.1-Ubuntu SMP Wed May 30
11:18:27 UTC 2018"
Info: FSCK version
  from "Linux version 4.13.0-45-generic (buildd@lgw01-amd64-011) (gcc version
5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.9)) #50~16.04.1-Ubuntu SMP Wed May
30 11:18:27 UTC 2018"
    to "Linux version 4.18.0-21-generic (buildd@lcy01-amd64-006) (gcc version
7.3.0 (Ubuntu 7.3.0-16ubuntu3)) #22~18.04.1-Ubuntu SMP Thu May 16 15:07:19 UTC
2019"
[update_superblock: 503] Info: Done to update superblock
Info: superblock features = 0 : 
Info: superblock encrypt level = 0, salt = 00000000000000000000000000000000
Info: total FS sectors = 131072 (64 MB)
Info: CKPT version = 3
[1]    13488 floating point exception (core dumped)  ./fsck/fsck.f2fs -f
/tmp/f2fs.img

[Location]
- build_curseg at fsck/mount.c:1589
  1589  array[i].zone = GET_ZONENO_FROM_SEGNO(sbi, segno);
- GET_ZONENO_FROM_SEGNO(sbi, segno) at fsck/f2fs.h:317
  318 ((segno / sbi->segs_per_sec) / sbi->secs_per_zone)
Causes division by zero error when sbi->secs_per_zone is corrupted to be 0.

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