On 2013年04月11日 12:08, Rusty Russell wrote:
> Chen Gang <[email protected]> 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.
>>
>>
>> Signed-off-by: Chen Gang <[email protected]>
>> Signed-off-by: Rusty Russell <[email protected]>
>
> ??!!! I never signed this off! I've never seen it before!
>
ok, thanks. I did not quite understand the rule of it.
originally, I think since you find it, I prefer to mention about you
in somewhere (e.g. mark as Reported-by ??)
could you provide additional suggestions for it ?
:-)
> Minor comments below:
>
I don't think they are 'minor comments'. I should improve them.
thank you for your work.
:-)
gchen.
>> -static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
>> +static unsigned int kallsyms_expand_symbol(unsigned int off,
>> + char *result, int maxlen)
>
> 'size_t maxlen' would be more explicit.
>
>> {
>> int len, skipped_first = 0;
>> const u8 *tptr, *data;
>> + char *begin = result;
>> /* Get the compressed symbol length from the first symbol byte. */
>> data = &kallsyms_names[off];
>> @@ -113,14 +116,16 @@ static unsigned int kallsyms_expand_symbol(unsigned
>> int off, char *result)
>> while (*tptr) {
>> if (skipped_first) {
>> - *result = *tptr;
>> - result++;
>> + *result++ = *tptr;
>> + if (result - begin == maxlen - 1)
>> + goto tail;
>
> You could just decrement maxlen instead, and handle maxlen == 0 at the
> same time:
>
> if (maxlen <= 1)
> goto tail;
> *result = *tptr;
> result++;
> maxlen--;
>
>> @@ -176,7 +181,7 @@ unsigned long kallsyms_lookup_name(const char *name)
>> unsigned int off;
>> for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
>> - off = kallsyms_expand_symbol(off, namebuf);
>> + off = kallsyms_expand_symbol(off, namebuf, sizeof(namebuf));
>> if (strcmp(namebuf, name) == 0)
>> return kallsyms_addresses[i];
>
> I prefer to use ARRAY_SIZE(namebuf) instead of sizeof(namebuf). That
> way we break compile if the declaration is changed from an array to a
> pointer one day.
>
> Same for the others.
>
> Thanks,
> Rusty.
>
>
--
Chen Gang
Asianux Corporation
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