linux-kernel - Re: [patch for-3.7] mm, mempolicy: fix printing stack contents in numa

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:	Tue, 16 Oct 2012 21:53:02 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Dave Jones <davej@...hat.com>, bhutchings@...arflare.com,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Hugh Dickins <hughd@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch for-3.7] mm, mempolicy: fix printing stack contents in numa_maps

On Tue, Oct 16, 2012 at 9:49 PM, David Rientjes <rientjes@...gle.com> wrote:
> On Tue, 16 Oct 2012, KOSAKI Motohiro wrote:
>
>> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
>> > index 0b78fb9..d04a8a5 100644
>> > --- a/mm/mempolicy.c
>> > +++ b/mm/mempolicy.c
>> > @@ -1536,9 +1536,8 @@ asmlinkage long compat_sys_mbind(compat_ulong_t start, compat_ulong_t len,
>> >   *
>> >   * Returns effective policy for a VMA at specified address.
>> >   * Falls back to @task or system default policy, as necessary.
>> > - * Current or other task's task mempolicy and non-shared vma policies
>> > - * are protected by the task's mmap_sem, which must be held for read by
>> > - * the caller.
>> > + * Current or other task's task mempolicy and non-shared vma policies must be
>> > + * protected by task_lock(task) by the caller.
>>
>> This is not correct. mmap_sem is needed for protecting vma. task_lock()
>> is needed to close vs exit race only when task != current. In other word,
>> caller must held both mmap_sem and task_lock if task != current.
>
> The comment is specifically addressing non-shared vma policies, you do not
> need to hold mmap_sem to access another thread's mempolicy.

I didn't say old comment is true. I just only your new comment also false.
--
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/