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From: Rusty Russell <rusty@rustcorp.com.au>
To: Chen Gang <gang.chen@asianux.com>
Cc: Stephen Boyd <sboyd@codeaurora.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2] kernel: kallsyms: memory override issue, need check destination buffer length
In-Reply-To: <51664B04.7000207@asianux.com>
References: <51662AC7.1090004@asianux.com> <87eheh4sls.fsf@rustcorp.com.au> <51664B04.7000207@asianux.com>
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Date: Mon, 15 Apr 2013 11:35:30 +0930
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Chen Gang <gang.chen@asianux.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>’

Cheers,
Rusty.
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