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

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Message-ID: <CAKYAXd-WLUQcyMAWd_R4PKRcciRh=faNnixv38abWmj7V=To9Q@mail.gmail.com>
Date:   Wed, 29 Nov 2023 23:09:54 +0900
From:   Namjae Jeon <linkinjeon@...nel.org>
To:     syzbot <syzbot+listb51f932ee38ecac1b05d@...kaller.appspotmail.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        sj1557.seo@...sung.com, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] Monthly exfat report (Nov 2023)

2023-11-28 6:03 GMT+09:00, syzbot
<syzbot+listb51f932ee38ecac1b05d@...kaller.appspotmail.com>:
> 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
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
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