On 2023/5/31 8:17, Baoquan He wrote:
> On 05/27/23 at 08:34pm, Zhen Lei wrote:
>> The check '(crashk_res.parent != NULL)' is added by
>> commit e05bd3367bd3 ("kexec: fix Oops in crash_shrink_memory()"), but it's
>> stale now. Because if 'crashk_res' is not reserved, it will be zero in
>> size and will be intercepted by the above 'if (new_size >= old_size)'.
>>
>> Ago:
>> if (new_size >= end - start + 1)
>>
>> Now:
>> old_size = (end == 0) ? 0 : end - start + 1;
>> if (new_size >= old_size)
>
> Hmm, I would strongly suggest we keep that check. Even though the
> current code like above can do the acutal checking, but its actual usage
> is not obvious for checking of crashk_res existence. In the future,
> someone may change above calculation and don't notice the hidden
> functionality at all behind the calculation. The cost of the check is
> almost zero, right?
The cost of the check is negligible. The only downside is that it's hard to
understand why it's added, and I only found out why by looking at the history
log. In my opinion, the above 'Now:' is the right fix.
>
>>
>> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
>> ---
>> kernel/kexec_core.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
>> index 22acee18195a591..d1ab139dd49035e 100644
>> --- a/kernel/kexec_core.c
>> +++ b/kernel/kexec_core.c
>> @@ -1137,7 +1137,7 @@ int crash_shrink_memory(unsigned long new_size)
>> end = start + new_size;
>> crash_free_reserved_phys_range(end, crashk_res.end);
>>
>> - if ((start == end) && (crashk_res.parent != NULL))
>> + if (start == end)
>> release_resource(&crashk_res);
>>
>> ram_res->start = end;
>> --
>> 2.25.1
>>
>
> .
>
--
Regards,
Zhen Lei
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