RE: [PATCH 9/9] netfilter: implement xt_cgroup cgroup2 path match

From: Jan Engelhardt
Date: Mon Nov 23 2015 - 12:56:03 EST



On Monday 2015-11-23 18:35, David Laight wrote:
>From: Florian Westphal
>> Sent: 21 November 2015 16:56
>> > +struct xt_cgroup_info_v1 {
>> > + char path[PATH_MAX];
>> > + __u32 classid;
>> > +
>> > + /* kernel internal data */
>> > + void *priv __attribute__((aligned(8)));
>> > +};
>>
>> Ahem. Am I reading this right? This struct is > 4k in size?
>> If so -- Ugh. Does sizeof(path) really have to be PATH_MAX?
>
>I've not looked at the use, but could you put 'char path[];'
>as the last member an require any allocations to be long enough
>to contain the actual path?

Oh, smart :) Yeah, ebt_among does something like that.
(.matchsize = -1, hint)

Except that the "priv" pointer seems to be ruining the fun here -
kernel vars have to be last, which collides with the requirements
for []-type members.
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