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: Mon, 26 Feb 2024 13:13:01 -0500 [thread overview]
Message-ID: <9bbc5b63-33e3-44de-8bce-4c59dcce5e92@rowland.harvard.edu> (raw)
In-Reply-To: <99b0fb1b-37b3-4da4-8129-e502ed8e479a@suse.com>
On Mon, Feb 26, 2024 at 11:59:06AM +0100, Oliver Neukum wrote:
> Hi,
>
> On 26.02.24 10:42, syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit: f2e367d6ad3b Merge tag 'for-6.8/dm-fix-3' of git://git.ker..
> > git tree: upstream
> > console+strace: https://syzkaller.appspot.com/x/log.txt?x=114e10e4180000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=eff9f3183d0a20dd
> > dashboard link: https://syzkaller.appspot.com/bug?extid=28748250ab47a8f04100
> > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1064b372180000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10aca6ac180000
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/c55ca1fdc5ad/disk-f2e367d6.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/4556a82fb4ed/vmlinux-f2e367d6.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/95338ed9dad1/bzImage-f2e367d6.xz
> >
> > The issue was bisected to:
> >
> > commit 321da3dc1f3c92a12e3c5da934090d2992a8814c
> > Author: Martin K. Petersen <martin.petersen@oracle.com>
> > Date: Tue Feb 13 14:33:06 2024 +0000
> >
> > scsi: sd: usb_storage: uas: Access media prior to querying device properties
>
> preliminary analysis:
>
> 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?
> 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.
> That raises two questions.
>
> 1) should we limit the read_before_ms flag to the cases transparent SCSI is used?
That won't help; the inquiry data will still be wrong.
> 2) does isd200_get_inquiry_data() need to validate what it reads?
Yes. At least to make sure that we're not going to divide by 0. This
means that id[ATA_ID_SECTORS] and id[ATA_ID_HEADS] must both be > 0.
Since they are 16-bit quantities, we don't have to worry about them
overflowing.
Do you want to submit a fix for syzbot to test?
Alan Stern
next prev parent reply other threads:[~2024-02-26 18:13 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 [this message]
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
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
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