Re: [PATCH v4 3/5] kasan: Add report for async mode

[Vincenzo Frascino <vincenzo.frascino@arm.com>]

On 1/19/21 1:04 PM, Catalin Marinas wrote:
> On Mon, Jan 18, 2021 at 06:30:31PM +0000, Vincenzo Frascino wrote:
>> KASAN provides an asynchronous mode of execution.
>>
>> Add reporting functionality for this mode.
>>
>> Cc: Dmitry Vyukov <dvyukov@google.com>
>> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
>> Cc: Alexander Potapenko <glider@google.com>
>> Cc: Andrey Konovalov <andreyknvl@google.com>
>> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
>> ---
>>  include/linux/kasan.h |  3 +++
>>  mm/kasan/report.c     | 16 ++++++++++++++--
>>  2 files changed, 17 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
>> index fe1ae73ff8b5..8f43836ccdac 100644
>> --- a/include/linux/kasan.h
>> +++ b/include/linux/kasan.h
>> @@ -336,6 +336,9 @@ static inline void *kasan_reset_tag(const void *addr)
>>  bool kasan_report(unsigned long addr, size_t size,
>>  		bool is_write, unsigned long ip);
>>  
>> +bool kasan_report_async(unsigned long addr, size_t size,
>> +			bool is_write, unsigned long ip);
> 
> We have no address, no size and no is_write information. Do we have a
> reason to pass all these arguments here? Not sure what SPARC ADI does
> but they may not have all this information either. We can pass ip as the
> point where we checked the TFSR reg but that's about it.
>

I kept the interface generic for future development and mainly to start a
discussion. I do not have a strong opinion either way. If Andrey agrees as well
I am happy to change it to what you are suggesting in v5.

>> +
>>  #else /* CONFIG_KASAN_SW_TAGS || CONFIG_KASAN_HW_TAGS */
>>  
>>  static inline void *kasan_reset_tag(const void *addr)
>> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
>> index c0fb21797550..946016ead6a9 100644
>> --- a/mm/kasan/report.c
>> +++ b/mm/kasan/report.c
>> @@ -388,11 +388,11 @@ static void __kasan_report(unsigned long addr, size_t size, bool is_write,
>>  	start_report(&flags);
>>  
>>  	print_error_description(&info);
>> -	if (addr_has_metadata(untagged_addr))
>> +	if (addr_has_metadata(untagged_addr) && (untagged_addr != 0))
>>  		print_tags(get_tag(tagged_addr), info.first_bad_addr);
>>  	pr_err("\n");
>>  
>> -	if (addr_has_metadata(untagged_addr)) {
>> +	if (addr_has_metadata(untagged_addr) && (untagged_addr != 0)) {
>>  		print_address_description(untagged_addr, get_tag(tagged_addr));
>>  		pr_err("\n");
>>  		print_memory_metadata(info.first_bad_addr);
>> @@ -419,6 +419,18 @@ bool kasan_report(unsigned long addr, size_t size, bool is_write,
>>  	return ret;
>>  }
>>  
>> +bool kasan_report_async(unsigned long addr, size_t size,
>> +			bool is_write, unsigned long ip)
>> +{
>> +	pr_info("==================================================================\n");
>> +	pr_info("KASAN: set in asynchronous mode\n");
>> +	pr_info("KASAN: some information might not be accurate\n");
>> +	pr_info("KASAN: fault address is ignored\n");
>> +	pr_info("KASAN: write/read distinction is ignored\n");
>> +
>> +	return kasan_report(addr, size, is_write, ip);
> 
> So just call kasan_report (0, 0, 0, ip) here.
> 

Fine by me.

-- 
Regards,
Vincenzo

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