Re: [PATCH v2] kernel: kallsyms: memory override issue, need checkdestination buffer length

From: Chen Gang
Date: Mon Apr 15 2013 - 00:30:58 EST

On 2013å04æ15æ 10:05, Rusty Russell wrote:
> Chen Gang <gang.chen@xxxxxxxxxxx> 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 âkallsyms_lookupâ:
> kernel/kallsyms.c:305:78: error: negative width in bit-field â<anonymous>â
> kernel/kallsyms.c: In function âlookup_symbol_nameâ:
> kernel/kallsyms.c:327:78: error: negative width in bit-field â<anonymous>â
> kernel/kallsyms.c: In function âlookup_symbol_attrsâ:
> kernel/kallsyms.c:346:69: error: negative width in bit-field â<anonymous>â

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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