Re: [syzbot] Monthly exfat report (Nov 2023)

From: Namjae Jeon
Date: Wed Nov 29 2023 - 09:10:01 EST


2023-11-28 6:03 GMT+09:00, syzbot
<syzbot+listb51f932ee38ecac1b05d@xxxxxxxxxxxxxxxxxxxxxxxxx>:
> Hello exfat maintainers/developers,
Hi,
>
> This is a 31-day syzbot report for the exfat subsystem.
> All related reports/information can be found at:
> https://syzkaller.appspot.com/upstream/s/exfat
>
> During the period, 1 new issues were detected and 0 were fixed.
> In total, 7 issues are still open and 12 have been fixed so far.
>
> Some of the still happening issues:
>
> Ref Crashes Repro Title
> <1> 225 No INFO: task hung in path_openat (7)
There is no reproducer and I couldn't find where it is connected to exfat.
>
> https://syzkaller.appspot.com/bug?extid=950a0cdaa2fdd14f5bdc
> <2> 150 No INFO: task hung in exfat_sync_fs
There is no reproducer... Let me know how to reproduce it.
This can happen when disk speed is very low and a lot of writes occur.
Is that so?

>
> https://syzkaller.appspot.com/bug?extid=205c2644abdff9d3f9fc
> <3> 119 Yes WARNING in drop_nlink (2)
I'm curious how this issue was classified as an exfat issue.
When looking at the backtrace, this issue appears to be an hfsplus issue.

hfsplus_unlink+0x3fe/0x790 fs/hfsplus/dir.c:381
hfsplus_rename+0xc8/0x1c0 fs/hfsplus/dir.c:547
vfs_rename+0xaba/0xde0 fs/namei.c:4844
>
> https://syzkaller.appspot.com/bug?extid=651ca866e5e2b4b5095b
> <4> 38 Yes INFO: task hung in exfat_write_inode
I could not reproduce this by using C reproducer provided by you.
Can you confirm that this really cannot be reproduced using it?

>
> https://syzkaller.appspot.com/bug?extid=2f73ed585f115e98aee8
> <5> 1 No UBSAN: shift-out-of-bounds in exfat_fill_super (2)
This is false alarm. ->sect_size_bits could not be greater than 12 by
the check below.

/*
* sect_size_bits could be at least 9 and at most 12.
*/
if (p_boot->sect_size_bits < EXFAT_MIN_SECT_SIZE_BITS ||
p_boot->sect_size_bits > EXFAT_MAX_SECT_SIZE_BITS) {
exfat_err(sb, "bogus sector size bits : %u",
p_boot->sect_size_bits);
return -EINVAL;
}
>
> https://syzkaller.appspot.com/bug?extid=d33808a177641a02213e
>
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