Date: Sun, 17 Dec 2017 16:08:08 -0500 From: Dan Langille <dan@langille.org> To: Warner Losh <imp@bsdimp.com> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: cannot access pass device from within jail Message-ID: <C19AEFEA-1105-4891-ABDE-B7222147D396@langille.org> In-Reply-To: <CANCZdfqWF1ckY58yp6sDGkJHxnwoyQB=nz1mnRKZe_mOM3H-gQ@mail.gmail.com> References: <E1314554-C8D0-4E8F-B8DB-E0B4D9DE325F@langille.org> <CANCZdfqWF1ckY58yp6sDGkJHxnwoyQB=nz1mnRKZe_mOM3H-gQ@mail.gmail.com>
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> On Dec 17, 2017, at 4:04 PM, Warner Losh <imp@bsdimp.com> wrote:
>
> What's the permissions of /dev/xpt0 in the jail? If it's not there I know
> at least camcontrol won't work. I've not used mtx, so I can't say if it's
> affected too or not.
I have tried both with and without xpt0. When I tried, it was:
# ls -l /dev/xpt0
crw------- 1 root operator 0x4c Dec 16 21:52 /dev/xpt0
>
> However, looking at the truss output:
>
> openat(AT_FDCWD,"/dev/pass7",O_RDWR|O_EXCL,00) ERR#1 'Operation not
> permitted'
> suggests something other than the canonical xpt0 issue else is going on. If
> we look at passopen in cam, I can see two exit paths:
>
> error = securelevel_gt(td->td_ucred, 1); if (error != 0) {...
> return error; }
> securelevel_gt is just "return (cr->cr_prison->pr_securelevel > level ?
> EPERM : 0);" which might be possible. What's the securelevel of the jail?
> Maybe this is going on somehow?
On the host:
$ sysctl kern.securelevel
kern.securelevel: -1
On the jail:
$ sysctl kern.securelevel
kern.securelevel: -1
>
> The second is basically
> if (((flags & FWRITE) == 0) || ((flags & FREAD) == 0)) {... return
> EPERM; }
> which isn't happening because of the O_RDWR in the truss output.
>
> The other possibility is that something above the pass driver is doing the
> check. I've not looked at that code path yet, buy you can see if it's
> making it to passopen() with dtrace and checking its return value. I don't
> see anything in how we register the device, though, that would suggest
> filtering it in jails.
>
> Warner
>
> On Sun, Dec 17, 2017 at 12:52 PM, Dan Langille <dan@langille.org> wrote:
>
>> Hello,
>>
>> What suggestions do you have for where I should look next? I'm happy to
>> start installing various builds of FreeBSD in order to track down which
>> commit caused this.
>>
>> I'm trying to access a tape library from within a jail running on a
>> FreeBSD 11.1 host. sa(4) devices are working (e.g. I can rewind nsa0).
>>
>> pass(4) devices (i.e. the tape changer ch0) are not working. This morning
>> I posted to -scsi@: https://lists.freebsd.org/pipermail/freebsd-scsi/2017-
>> December/007608.html
>>
>> The device appears in the jail and has appropriate permissions. This
>> access was granted
>> via /etc/devfs.rules using the same approach I used for FreeBSD 10.3
>>
>> The permissions in the jail:
>>
>> [root@bacula-sd-02 ~]# ls -l /dev/pass7
>> crw------- 1 root operator 0x74 Dec 16 21:52 /dev/pass7
>>
>> The command in the jail:
>>
>> [root@bacula-sd-02 ~]# mtx -f /dev/pass7 status
>> cannot open SCSI device '/dev/pass7' - Operation not permitted
>>
>> Here is the truss output of the command in question:
>> https://gist.github.com/dlangille/b80ee804b8080e1cbf5b5ab67f0bdabe
>>
>> Thank you.
>>
>> --
>> Dan Langille - BSDCan / PGCon
>> dan@langille.org
>>
>>
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