From: Alan Stern <stern@rowland.harvard.edu>
To: Oliver Neukum <oneukum@suse.com>
Cc: syzbot <syzbot+28748250ab47a8f04100@syzkaller.appspotmail.com>,
bvanassche@acm.org, emilne@redhat.com,
gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
linux-usb@vger.kernel.org, martin.petersen@oracle.com,
syzkaller-bugs@googlegroups.com, tasos@tasossah.com,
usb-storage@lists.one-eyed-alien.net
Subject: Re: [syzbot] [usb-storage?] divide error in isd200_ata_command
Date: Wed, 28 Feb 2024 14:23:25 -0500 [thread overview]
Message-ID: <d5328312-4cd0-426f-8db4-29d67790c213@rowland.harvard.edu> (raw)
In-Reply-To: <12b30393-0b4b-400e-828b-231901d8933b@suse.com>
On Wed, Feb 28, 2024 at 05:20:29PM +0100, Oliver Neukum wrote:
> On 26.02.24 19:13, Alan Stern wrote:
>
> > > It oopses here:
> > >
> > > } else {
> > > if (!id[ATA_ID_SECTORS] || !id[ATA_ID_HEADS])
> > > goto too_early;
> >
> > Those two lines are debugging code you added, right?
>
> Yes, sorry about that.
>
> >
> > > sectnum = (u8)((lba % id[ATA_ID_SECTORS]) + 1);
> > > cylinder = (u16)(lba / (id[ATA_ID_SECTORS] *
> > > id[ATA_ID_HEADS]));
> > >
> > > in isd200_scsi_to_ata() because it must not be called before isd200_get_inquiry_data()
> > > has completed.
> >
> > It can't be; isd200_get_inquiry_data is called by isd200_Initialization
> > during probe before any SCSI commands are transmitted.
>
> So, you are concluding that the bisection is spurious because
> without that patch the SCSI layer would see a capacity of zero
> and not even try to read anything?
I don't know. My guess is that without this patch, the test would fail
for some reason before the SCSI layer has a chance to issue a READ command.
Maybe because of a zero capacity, like you said, or maybe something
else.
Whatever the reason, it looks like Martin's commit merely exposed a
problem which has existed all along.
Alan Stern
next prev parent reply other threads:[~2024-02-28 19:23 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-26 9:42 [syzbot] [usb-storage?] divide error in isd200_ata_command syzbot
2024-02-26 10:59 ` Oliver Neukum
2024-02-26 18:13 ` Alan Stern
2024-02-27 2:46 ` Martin K. Petersen
2024-02-27 3:05 ` Alan Stern
2024-02-28 16:20 ` Oliver Neukum
2024-02-28 19:23 ` Alan Stern [this message]
2024-02-27 19:36 ` Alan Stern
2024-02-28 5:20 ` syzbot
2024-02-28 16:12 ` Alan Stern
2024-02-28 16:13 ` syzbot
2024-02-28 16:52 ` Aleksandr Nogikh
2024-02-28 19:18 ` Alan Stern
2024-02-29 0:33 ` syzbot
2024-02-29 19:30 ` [PATCH] USB: usb-storage: Prevent divide-by-0 " Alan Stern
2024-03-01 1:11 ` Martin K. Petersen
2024-03-01 11:36 ` PrasannaKumar Muralidharan
2024-02-29 15:40 ` [syzbot] [usb-storage?] divide " Aleksandr Nogikh
2024-02-29 16:12 ` Alan Stern
2024-02-29 17:57 ` Aleksandr Nogikh
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=d5328312-4cd0-426f-8db4-29d67790c213@rowland.harvard.edu \
--to=stern@rowland.harvard.edu \
--cc=bvanassche@acm.org \
--cc=emilne@redhat.com \
--cc=gregkh@linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=martin.petersen@oracle.com \
--cc=oneukum@suse.com \
--cc=syzbot+28748250ab47a8f04100@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
--cc=tasos@tasossah.com \
--cc=usb-storage@lists.one-eyed-alien.net \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).