SYZFAIL: tun: read failed

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ad110f3f2f3f In the next major bump, some BN macros will b..
git tree: openbsd
console output: https://syzkaller.appspot.com/x/log.txt?x=137d2ae5b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=bf87b6915a88cd0d
dashboard link: https://syzkaller.appspot.com/bug?extid=682dad6055938e287d19

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+682dad...@syzkaller.appspotmail.com

SYZFAIL: tun: read failed
(errno 5: Input/output error)
SYZFAIL: child failed
(errno 0: Undefined error: 0)


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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 78636d64e252 Respond to OSC 4 query.
git tree: openbsd
console output: https://syzkaller.appspot.com/x/log.txt?x=167f9da9b00000

kernel config: https://syzkaller.appspot.com/x/.config?x=bf87b6915a88cd0d
dashboard link: https://syzkaller.appspot.com/bug?extid=682dad6055938e287d19

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=137d684db00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+682dad...@syzkaller.appspotmail.com

SYZFAIL: tun: read failed
(errno 5: Input/output error)
SYZFAIL: child failed
(errno 0: Undefined error: 0)

ifconfig: SIOCIFDESTROY: Device not configured

SYZFAIL: tun: read failed
(errno 5: Input/output error)
SYZFAIL: child failed
(errno 0: Undefined error: 0)

login:

[Anton Lindqvist]

On Mon, Dec 06, 2021 at 02:24:29PM -0800, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: ad110f3f2f3f In the next major bump, some BN macros will b..
> git tree: openbsd
> console output: https://syzkaller.appspot.com/x/log.txt?x=137d2ae5b00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=bf87b6915a88cd0d
> dashboard link: https://syzkaller.appspot.com/bug?extid=682dad6055938e287d19
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+682dad...@syzkaller.appspotmail.com
>
> SYZFAIL: tun: read failed
> (errno 5: Input/output error)
> SYZFAIL: child failed
> (errno 0: Undefined error: 0)

It ends up in dead_read() since the underlying vnode is revoked through
`ifconfig tunX destroy'. Looking at other panics, I can see mulitple
syz-exector processes running. Do all of them start with procid = 0?
That would explain it as interfaces are not unique, each syz-executor
process would either need an exclusive range of interfaces or another
method of creating the interface path:
/dev/tun{${syz-executor-procid} * MAX_TUN + procid}