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Date: Tue, 31 Mar 2015 15:45:54 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Heinrich Schuchardt <xypron.glpk@gmx.de>
Cc: Michal Nazarewicz <mina86@mina86.com>, Ingo Molnar <mingo@kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
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        Eric B Munson <emunson@akamai.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Sam Ravnborg <sam@ravnborg.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] sysctl: detect overflows when converting to int
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On Sun, 29 Mar 2015 21:28:29 +0200 Heinrich Schuchardt <xypron.glpk@gmx.de> wrote:

> When converting unsigned long to int overflows may occur.
> These currently are not detected when writing to the sysctl
> file system.
> 
> E.g. on a system where int has 32 bits and long has 64 bits
>   echo 0x800001234 > /proc/sys/kernel/threads-max
> has the same effect as
>   echo 0x1234 > /proc/sys/kernel/threads-max
> 
> The patch adds the missing check in do_proc_dointvec_conv.
> 
> With the patch an overflow will result in an error EINVAL when
> writing to the the sysctl file system.

hm, why fix this?  There's a small risk of breaking
accidentally-working userspace, but I expect we can live with that.

But how big a problem is this, really?  This behaviour is quite
expected, after all.