linux-kernel - Re: [BUG] kernel BUG at mm/vmacache.c:85!

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1398723290.25549.20.camel@buesod1.americas.hpqcorp.net>
Date:	Mon, 28 Apr 2014 15:14:50 -0700
From:	Davidlohr Bueso <davidlohr@...com>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Linux MM <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rik van Riel <riel@...hat.com>,
	Michel Lespinasse <walken@...gle.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [BUG] kernel BUG at mm/vmacache.c:85!

On Mon, 2014-04-28 at 15:05 -0700, Hugh Dickins wrote:
> On Mon, 28 Apr 2014, Linus Torvalds wrote:
> > On Mon, Apr 28, 2014 at 2:20 PM, Linus Torvalds
> > <torvalds@...ux-foundation.org> wrote:
> > >
> > > That said, the bug does seem to be that some path doesn't invalidate
> > > the vmacache sufficiently, or something inserts a vmacache entry into
> > > the current process when looking up a remote process or whatever.
> > > Davidlohr, ideas?
> > 
> > Maybe we missed some use_mm() call. That will change the current mm
> > without flushing the vma cache. The code considers kernel threads to
> > be bad targets for vma caching for this reason (and perhaps others),
> > but maybe we missed something.
> > 
> > I wonder if we should just invalidate the vma cache in use_mm(), and
> > remote the "kernel tasks are special" check.
> > 
> > Srivatsa, are you doing something peculiar on that system that would
> > trigger this? I see some kdump failures in the log, anything else?
> 
> I doubt that the vmacache has anything to do with the real problem
> (though it *might* suggest that vmacache is less robust than what
> it replaced - maybe).  The log is so full of userspace SIGSEGVs
> and General Protection faults, it looks like userspace was utterly
> broken by some kernel bug messing up the address space.

I think that returning some stale/bogus vma is causing those segfaults
in udev. It shouldn't occur in a normal scenario. What puzzles me is
that it's not always reproducible. This makes me wonder what else is
going on...

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/