linux-kernel - Re: [PATCH 2/5] uprobes: suppress uprobe

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]

Message-ID: <20120712055750.GC3598@linux.vnet.ibm.com>
Date:	Thu, 12 Jul 2012 11:27:51 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] uprobes: suppress uprobe_munmap() from mmput()

* Oleg Nesterov <oleg@...hat.com> [2012-07-08 22:30:03]:

> uprobe_munmap() does get_user_pages() and it is also called from
> the final mmput()->exit_mmap() path. This slows down exit/mmput()
> for no reason, and I think  it is simply dangerous/wrong to try to
> fault-in a page into the dying mm. If nothing else, this happens
> after the last sync_mm_rss(), afaics handle_mm_fault() can change
> the task->rss_stat and make the subsequent check_mm() unhappy.
> 
> Change uprobe_munmap() to check mm->mm_users != 0.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Acked-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>

> ---
>  kernel/events/uprobes.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index a93b6df..47c4e24 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1082,6 +1082,9 @@ void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned lon
>  	if (!atomic_read(&uprobe_events) || !valid_vma(vma, false))
>  		return;
> 
> +	if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */
> +		return;
> +
>  	if (!atomic_read(&vma->vm_mm->uprobes_state.count))
>  		return;
> 
> -- 
> 1.5.5.1
> 

--
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/