linux-kernel - Re: mm: mmap_sem lock assertion failure in __mlock_vma_pages

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: <1394568453.2786.28.camel@buesod1.americas.hpqcorp.net>
Date:	Tue, 11 Mar 2014 13:07:33 -0700
From:	Davidlohr Bueso <davidlohr@...com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michel Lespinasse <walken@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: mm: mmap_sem lock assertion failure in __mlock_vma_pages_range

On Tue, 2014-03-11 at 15:39 -0400, Sasha Levin wrote:
> Hi all,
> 
> I've ended up deleting the log file by mistake, but this bug does seem to be important
> so I'd rather not wait before the same issue is triggered again.
> 
> The call chain is:
> 
> 	mlock (mm/mlock.c:745)
> 		__mm_populate (mm/mlock.c:700)
> 			__mlock_vma_pages_range (mm/mlock.c:229)
> 				VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));

So __mm_populate() is only called by mlock(2) and this VM_BUG_ON seems
wrong as we call it without the lock held:

	up_write(&current->mm->mmap_sem);
	if (!error)
		error = __mm_populate(start, len, 0);
	return error;
}

> 
> It seems to be a rather simple trace triggered from userspace. The only recent patch
> in the area (that I've noticed) was "mm/mlock: prepare params outside critical region".
> I've reverted it and trying to testing without it.

Odd, this patch should definitely *not* cause this. In any case every
operation removed from the critical region is local to the function:

	lock_limit = rlimit(RLIMIT_MEMLOCK);
	lock_limit >>= PAGE_SHIFT;
	locked = len >> PAGE_SHIFT;

	down_write(&current->mm->mmap_sem);

--
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/