linux-kernel - Re: [PATCH v2] kernel: kallsyms: memory override issue, need check destination buffer length

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Date:	Mon, 15 Apr 2013 12:30:11 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Stephen Boyd <sboyd@...eaurora.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] kernel: kallsyms: memory override issue, need check
 destination buffer length

On 2013年04月15日 10:05, Rusty Russell wrote:
> Chen Gang <gang.chen@...anux.com> writes:
>> >   We don't export any symbols > 128 characters, but if we did then
>> >   kallsyms_expand_symbol() would overflow the buffer handed to it.
>> >   So we need check destination buffer length when copying.
>> >
>> >   the related test:
>> >     if we define an EXPORT function which name more than 128.
>> >     will panic when call kallsyms_lookup_name by init_kprobes on booting.
>> >     after check the length (provide this patch), it is ok.
>> >
>> >   Implementaion:
>> >     add additional destination buffer length parameter (maxlen)
>> >     if uncompressed string is too long (>= maxlen), it will be truncated.
>> >     not check the parameters whether valid, since it is a static function.
> Found a bug already:
> 
> kernel/kallsyms.c: In function ‘kallsyms_lookup’:
> kernel/kallsyms.c:305:78: error: negative width in bit-field ‘<anonymous>’
> kernel/kallsyms.c: In function ‘lookup_symbol_name’:
> kernel/kallsyms.c:327:78: error: negative width in bit-field ‘<anonymous>’
> kernel/kallsyms.c: In function ‘lookup_symbol_attrs’:
> kernel/kallsyms.c:346:69: error: negative width in bit-field ‘<anonymous>’
> 

  oh... it is my fault, I will send v3.

  I only tested kallsyms_on_each_symbol and kallsyms_lookup_name (they
were of cause OK). , not test others.

  ARRAY_SIZE is really valuable to help find bugs.

  and next, after code changes, I should compile it again, at least.

  :-)


> Cheers,


-- 
Chen Gang

Asianux Corporation
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