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  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Sun, 9 Mar 2014 18:09:09 +0100
From:	Oleg Nesterov <>
To:	Linus Torvalds <>
Cc:	Davidlohr Bueso <>,
	Andrew Morton <>,
	Ingo Molnar <>,
	Peter Zijlstra <>,
	Michel Lespinasse <>,
	Mel Gorman <>, Rik van Riel <>,
	KOSAKI Motohiro <>,
	Davidlohr Bueso <>,
	Linux Kernel Mailing List <>
Subject: Re: [PATCH v4] mm: per-thread vma caching

On 03/09, Linus Torvalds wrote:
> On Sun, Mar 9, 2014 at 5:57 AM, Oleg Nesterov <> wrote:
> >
> > No, dup_task_struct() is obviously lockless. And the new child is not yet
> > visible to for_each_process_thread().
> Ok, then the siimple approach is to just do
>     /* Did we miss an invalidate event? *
>     if (mm->seqcount < tsk->seqcount)
>         clear_vma_cache();
> after making the new thread visible.
> Then the "race" becomes one of "we cannot have 4 billion mmap/munmap
> events in other threads while we're setting up a new thread",

But it's not the "while we're setting up a new thread", it is "since
vmacache_valid() was called list time". And the cloning task can just
sleep(A_LOT) and then do CLONE_VM.

Of course, of course, this race is pute theoretical anyway. But imho
makes sense to fix anyway, and the natural/trivial approach is just to
move vmacache_flush(tsk) from dup_mm() to copy_mm(), right after the
"if (!oldmm)" check.


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists