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

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Message-ID: <87y5ck8s5x.fsf@rustcorp.com.au>
Date:	Mon, 15 Apr 2013 11:35:30 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Chen Gang <gang.chen@...anux.com>
Cc:	Stephen Boyd <sboyd@...eaurora.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] kernel: kallsyms: memory override issue, need check destination buffer length

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>’

Cheers,
Rusty.
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