linux-kernel - Re: Programs die when max_map

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Date:	Fri, 27 Nov 2009 14:30:24 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	jengelh@...ozas.de, linux-kernel@...r.kernel.org
Subject: Re: Programs die when max_map_count is too large

On Fri, Nov 27, 2009 at 12:48 AM, Alexey Dobriyan <adobriyan@...il.com> wrote:
>> IMO, the problem is 'sysctl_max_map_count' is actually signed int,
>> while when writing to it, the value is treated as unsigned.
>
> The problem is the loop in simple_strtoul(), some people were so afraid
> to touch so they even came up with strict_* variants.
>
>> A better fix which I could imagine is to fix sysctl to understand
>> signed int's.
>
>        -       int map_count;
>        +       unsigned int map_count;
>
> This is incomplete at least.
>

Yeah, perhaps.

I got a better fix, but only for max_map_count. Please check it below.

(Sorr for attatching it, gmail's IMAP sucks.)

----------------->

Make negative values for 'max_map_count' invalid, they are meaningless.
And avoid overflow.

I already tested this.

Signed-off-by: WANG Cong <xiyou.wangcong@...il.com>
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View attachment "kernel-sysctl-max-map-count-overflow.diff" of type "text/plain" (392 bytes)