linux-kernel - Re: possible deadlock in process

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Message-ID: <20190715163459.GB728@sol.localdomain>
Date:   Mon, 15 Jul 2019 09:34:59 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     Mimi Zohar <zohar@...ux.ibm.com>,
        syzbot <syzbot+5ab61747675a87ea359d@...kaller.appspotmail.com>,
        dmitry.kasatkin@...il.com, jmorris@...ei.org,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, serge@...lyn.com,
        syzkaller-bugs@...glegroups.com, zohar@...ux.vnet.ibm.com
Subject: Re: possible deadlock in process_measurement

On Thu, Jul 11, 2019 at 12:50:13PM -0700, Eric Biggers wrote:
> Hi Mimi,
> 
> On Thu, Jul 11, 2019 at 10:14:36AM -0400, Mimi Zohar wrote:
> > Hi Eric,
> > 
> > On Mon, 2019-06-03 at 09:35 -0700, syzbot wrote:
> > > syzbot has found a reproducer for the following crash on:
> > > 
> > > HEAD commit:    3c09c195 Add linux-next specific files for 20190531
> > > git tree:       linux-next
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=10f61a0ea00000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=6cfb24468280cd5c
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=5ab61747675a87ea359d
> > > compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> > > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=177c3d16a00000
> > > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14ec01baa00000
> > > 
> > 
> > This reproducer seems like it is similar, but the cause is different
> > than the original report.  One has to do with overlayfs, while the
> > other has to do with ext4, mprotect/mmap.  I assume in both cases an
> > IMA policy was required to trigger the locking bug.  What type of IMA
> > policy are you using?
> > 
> > Do we need to differentiate the two reports?  Is the "last occurred"
> > notification for the overlay, for mprotect, or both?  Please Cc the
> > overlay mailing list on the overlay aspect.
> 
> AFAICS, syzbot boots all kernels with "ima_policy=tcb" on the command line.
> And I don't think anything in userspace changes the IMA policy.
> 
> It's not unusual for multiple underlying bugs to get mixed into the same syzbot
> bug.  syzbot doesn't know that one "possible deadlock in process_measurement" is
> different from another.  "Last occurred" is for any crash that appeared as such.
> 
> This just needs to be handled the best we can.  Sometimes all the bugs can be
> fixed; sometimes they've already been fixed; or sometimes it's easiest to fix
> just one and then mark the syzbot bug as fixed, and syzbot will report it again
> it's still occurring for some other reason.
> 
> - Eric

Invalidating this bug report as per the discussion at
https://lkml.kernel.org/linux-integrity/1563122888.4539.119.camel@linux.ibm.com/T/#mcd083826e5843f048c914c56a4e82147fc211704

#syz invalid

For future reference, anyone can update the status of syzbot bugs; no need to
ask me to do it.  See https://goo.gl/tpsmEJ#status

- Eric