linux-kernel - Re: [PATCH 2/3] uprobes: __copy_insn() should ensure a

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Message-ID: <20120615062534.GB3811@linux.vnet.ibm.com>
Date:	Fri, 15 Jun 2012 11:55:34 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Hugh Dickins <hughd@...gle.com>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] uprobes: __copy_insn() should ensure
 a_ops->readpage	!= NULL

* Oleg Nesterov <oleg@...hat.com> [2012-06-07 19:00:18]:

> __copy_insn() blindly calls read_mapping_page(), this will crash
> the kernel if ->readpage == NULL, add the necessary check. For
> example, hugetlbfs_aops->readpage is NULL. Perhaps we should change
> read_mapping_page() instead.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> ---
>  kernel/events/uprobes.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 48d53af..9c53bc2 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -616,6 +616,8 @@ __copy_insn(struct address_space *mapping, struct vm_area_struct *vma, char *ins
> 
>  	if (!filp)
>  		return -EINVAL;
> +	if (!mapping->a_ops->readpage)
> +		return -EIO;

Nit: Should there be a blank line before the if. Ingo had insisted on
these coding style changes.

>  	idx = (unsigned long)(offset >> PAGE_CACHE_SHIFT);
>  	off1 = offset &= ~PAGE_MASK;

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

-- 
Thanks and Regards
Srikar

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