netdev - Re: [RFC] Handle error writing UINT

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Date:	Tue, 14 Jun 2016 14:36:41 -0600
From:	subashab@...eaurora.org
To:	Heinrich Schuchardt <xypron.glpk@....de>
Cc:	eric.dumazet@...il.com, netdev@...r.kernel.org,
	netdev-owner@...r.kernel.org
Subject: Re: [RFC] Handle error writing UINT_MAX to u32 fields

On 2016-06-12 20:30, subashab@...eaurora.org wrote:
>> The suggested change would extend the usable range of positive numbers
>> by one bit only. As many systems are 64 bit this does not seem forward
>> looking.
>> 
>> I would prefer to have a routine that can handle 64 bit integers with
>> limits (let's call it proc_doint64vec_minmax) which uses fields extra1
>> and extra2 of ctl_table as min and max.
>> 
>> Then set xfrm_table[].extra1 = 0 and xfrm_table[].extra2 = UINT_MAX if
>> you need a result in the u32 range.
>> 
> 
> Thanks Heinrich. Do you think we can use proc_doulongvec_minmax for 
> this?

Actually proc_doulongvec_minmax does not work here.
I would expect similar problems due to casting if we use u64 
(proc_doint64vec_minmax) here.

static int __do_proc_doulongvec_minmax(void *data, struct ctl_table 
*table, int write,
{
	unsigned long *i, *min, *max;
	int vleft, first = 1, err = 0;

	i = (unsigned long *) data;   //This cast is causing to read beyond the 
size of data (u32)
	min = (unsigned long *) table->extra1;
	max = (unsigned long *) table->extra2;
	vleft = table->maxlen / sizeof(unsigned long); //vleft is 0 because 
maxlen is sizeof(u32) which is lesser than sizeof(unsigned long) on 
x86_64.

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