* Re: Fw: [PATCH] lib/kstrtox.c Stop parsing integer on overflow
[not found] <20150217161724.65a9ff577f84917497d61b4e@linux-foundation.org>
@ 2015-02-18 7:44 ` Alexey Dobriyan
2015-02-19 17:53 ` Anshul Garg
0 siblings, 1 reply; 3+ messages in thread
From: Alexey Dobriyan @ 2015-02-18 7:44 UTC (permalink / raw)
To: Andrew Morton; +Cc: aksgarg1989, linux-kernel
On Tue, Feb 17, 2015 at 04:17:24PM -0800, Andrew Morton wrote:
> ?
>
> Begin forwarded message:
>
> Date: Mon, 16 Feb 2015 10:48:50 -0800
> From: Anshul Garg <aksgarg1989@gmail.com>
> To: linux-kernel@vger.kernel.org
> Cc: aksgarg1989@gmail.com, anshul.g@samsung.com, torvalds@linux-foundation.org
> Subject: [PATCH] lib/kstrtox.c Stop parsing integer on overflow
>
>
> From: Anshul Garg <aksgarg1989@gmail.com>
>
> While converting string representation to integer
> break the loop if overflow is detected.
>
> Signed-off-by: Anshul Garg <aksgarg1989@gmail.com>
> ---
> lib/kstrtox.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/lib/kstrtox.c b/lib/kstrtox.c
> index ec8da78..6f30209 100644
> --- a/lib/kstrtox.c
> +++ b/lib/kstrtox.c
> @@ -70,8 +70,10 @@ unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long
> * it in the max base we support (16)
> */
> if (unlikely(res & (~0ull << 60))) {
> - if (res > div_u64(ULLONG_MAX - val, base))
> + if (res > div_u64(ULLONG_MAX - val, base)) {
> overflow = 1;
> + break;
> + }
> }
> res = res * base + val;
> rv++;
The _notion_ of a patch is OK if you want EVERY simple_strtoull() call
to stop parsing past overflow right now. It SHOULD have done so from day 1,
but it doesn't do that.
When I wrote kstrto*() code I deliberatedly didn't break this bug
because of the sheer number of call sites.
If you are OK with changing bug-for-bug compatibility,
then patch simply need to delete overflow detection code.
Alexey
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Fw: [PATCH] lib/kstrtox.c Stop parsing integer on overflow
2015-02-18 7:44 ` Fw: [PATCH] lib/kstrtox.c Stop parsing integer on overflow Alexey Dobriyan
@ 2015-02-19 17:53 ` Anshul Garg
2015-02-20 11:08 ` Alexey Dobriyan
0 siblings, 1 reply; 3+ messages in thread
From: Anshul Garg @ 2015-02-19 17:53 UTC (permalink / raw)
To: Alexey Dobriyan; +Cc: Andrew Morton, Linux Kernel Mailing List
On Wed, Feb 18, 2015 at 1:14 PM, Alexey Dobriyan <adobriyan@gmail.com> wrote:
> On Tue, Feb 17, 2015 at 04:17:24PM -0800, Andrew Morton wrote:
>> ?
>>
>> Begin forwarded message:
>>
>> Date: Mon, 16 Feb 2015 10:48:50 -0800
>> From: Anshul Garg <aksgarg1989@gmail.com>
>> To: linux-kernel@vger.kernel.org
>> Cc: aksgarg1989@gmail.com, anshul.g@samsung.com, torvalds@linux-foundation.org
>> Subject: [PATCH] lib/kstrtox.c Stop parsing integer on overflow
>>
>>
>> From: Anshul Garg <aksgarg1989@gmail.com>
>>
>> While converting string representation to integer
>> break the loop if overflow is detected.
>>
>> Signed-off-by: Anshul Garg <aksgarg1989@gmail.com>
>> ---
>> lib/kstrtox.c | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/lib/kstrtox.c b/lib/kstrtox.c
>> index ec8da78..6f30209 100644
>> --- a/lib/kstrtox.c
>> +++ b/lib/kstrtox.c
>> @@ -70,8 +70,10 @@ unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long
>> * it in the max base we support (16)
>> */
>> if (unlikely(res & (~0ull << 60))) {
>> - if (res > div_u64(ULLONG_MAX - val, base))
>> + if (res > div_u64(ULLONG_MAX - val, base)) {
>> overflow = 1;
>> + break;
>> + }
>> }
>> res = res * base + val;
>> rv++;
>
> The _notion_ of a patch is OK if you want EVERY simple_strtoull() call
> to stop parsing past overflow right now. It SHOULD have done so from day 1,
> but it doesn't do that.
>
> When I wrote kstrto*() code I deliberatedly didn't break this bug
> because of the sheer number of call sites.
>
> If you are OK with changing bug-for-bug compatibility,
> then patch simply need to delete overflow detection code.
>
> Alexey
I think this patch won't break any existing module using this function.
because this function sets KSTRTOX_OVERFLOW as error status.
which is checked by calling function to determine whether value is correct
or not.
If this flag is set we can simply discard the parsed value.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Fw: [PATCH] lib/kstrtox.c Stop parsing integer on overflow
2015-02-19 17:53 ` Anshul Garg
@ 2015-02-20 11:08 ` Alexey Dobriyan
0 siblings, 0 replies; 3+ messages in thread
From: Alexey Dobriyan @ 2015-02-20 11:08 UTC (permalink / raw)
To: Anshul Garg; +Cc: Andrew Morton, Linux Kernel Mailing List
On Thu, Feb 19, 2015 at 8:53 PM, Anshul Garg <aksgarg1989@gmail.com> wrote:
> On Wed, Feb 18, 2015 at 1:14 PM, Alexey Dobriyan <adobriyan@gmail.com> wrote:
>> On Tue, Feb 17, 2015 at 04:17:24PM -0800, Andrew Morton wrote:
>>> ?
>>>
>>> Begin forwarded message:
>>>
>>> Date: Mon, 16 Feb 2015 10:48:50 -0800
>>> From: Anshul Garg <aksgarg1989@gmail.com>
>>> To: linux-kernel@vger.kernel.org
>>> Cc: aksgarg1989@gmail.com, anshul.g@samsung.com, torvalds@linux-foundation.org
>>> Subject: [PATCH] lib/kstrtox.c Stop parsing integer on overflow
>>>
>>>
>>> From: Anshul Garg <aksgarg1989@gmail.com>
>>>
>>> While converting string representation to integer
>>> break the loop if overflow is detected.
>>>
>>> Signed-off-by: Anshul Garg <aksgarg1989@gmail.com>
>>> ---
>>> lib/kstrtox.c | 4 +++-
>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/lib/kstrtox.c b/lib/kstrtox.c
>>> index ec8da78..6f30209 100644
>>> --- a/lib/kstrtox.c
>>> +++ b/lib/kstrtox.c
>>> @@ -70,8 +70,10 @@ unsigned int _parse_integer(const char *s, unsigned int base, unsigned long long
>>> * it in the max base we support (16)
>>> */
>>> if (unlikely(res & (~0ull << 60))) {
>>> - if (res > div_u64(ULLONG_MAX - val, base))
>>> + if (res > div_u64(ULLONG_MAX - val, base)) {
>>> overflow = 1;
>>> + break;
>>> + }
>>> }
>>> res = res * base + val;
>>> rv++;
>>
>> The _notion_ of a patch is OK if you want EVERY simple_strtoull() call
>> to stop parsing past overflow right now. It SHOULD have done so from day 1,
>> but it doesn't do that.
>>
>> When I wrote kstrto*() code I deliberatedly didn't break this bug
>> because of the sheer number of call sites.
>>
>> If you are OK with changing bug-for-bug compatibility,
>> then patch simply need to delete overflow detection code.
>>
>> Alexey
>
> I think this patch won't break any existing module using this function.
> because this function sets KSTRTOX_OVERFLOW as error status.
>
> which is checked by calling function to determine whether value is correct
> or not.
>
> If this flag is set we can simply discard the parsed value.
Which is my previous email is all about.
If you discard, every single simple_strto*() call will change its behaviour.
If you're OK with that, patch is incomplete.
Alexey
^ permalink raw reply [flat|nested] 3+ messages in thread
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[not found] <20150217161724.65a9ff577f84917497d61b4e@linux-foundation.org>
2015-02-18 7:44 ` Fw: [PATCH] lib/kstrtox.c Stop parsing integer on overflow Alexey Dobriyan
2015-02-19 17:53 ` Anshul Garg
2015-02-20 11:08 ` Alexey Dobriyan
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