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Date: Thu, 02 Apr 2020 12:04:44 -0500
From: ebiederm@...ssion.com (Eric W. Biederman)
To: Alexey Gladkov <gladkov.alexey@...il.com>
Cc: LKML <linux-kernel@...r.kernel.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Linux API <linux-api@...r.kernel.org>, Linux FS Devel <linux-fsdevel@...r.kernel.org>, Linux Security Module <linux-security-module@...r.kernel.org>, Akinobu Mita <akinobu.mita@...il.com>, Alexander Viro <viro@...iv.linux.org.uk>, Alexey Dobriyan <adobriyan@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, Andy Lutomirski <luto@...nel.org>, Daniel Micay <danielmicay@...il.com>, Djalal Harouni <tixxdz@...il.com>, "Dmitry V . Levin" <ldv@...linux.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Ingo Molnar <mingo@...nel.org>, "J . Bruce Fields" <bfields@...ldses.org>, Jeff Layton <jlayton@...chiereds.net>, Jonathan Corbet <corbet@....net>, Kees Cook <keescook@...omium.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Oleg Nesterov <oleg@...hat.com>, David Howells <dhowells@...hat.com>
Subject: Re: [PATCH v10 8/9] proc: use human-readable values for hidehid
Alexey Gladkov <gladkov.alexey@...il.com> writes:
> On Thu, Apr 02, 2020 at 11:05:21AM -0500, Eric W. Biederman wrote:
>> Alexey Gladkov <gladkov.alexey@...il.com> writes:
>>
>> > The hidepid parameter values are becoming more and more and it becomes
>> > difficult to remember what each new magic number means.
>>
>> In principle I like this change. In practice I think you have just
>> broken ABI compatiblity with the new mount ABI.
>>
>> In particular the following line seems broken.
>>
>> > diff --git a/fs/proc/root.c b/fs/proc/root.c
>> > index dbcd96f07c7a..ba782d6e6197 100644
>> > --- a/fs/proc/root.c
>> > +++ b/fs/proc/root.c
>> > @@ -45,7 +45,7 @@ enum proc_param {
>> >
>> > static const struct fs_parameter_spec proc_fs_parameters[] = {
>> > fsparam_u32("gid", Opt_gid),
>> > - fsparam_u32("hidepid", Opt_hidepid),
>> > + fsparam_string("hidepid", Opt_hidepid),
>> > fsparam_string("subset", Opt_subset),
>> > {}
>> > };
>>
>> As I read fs_parser.c fs_param_is_u32 handles string inputs and turns them
>> into numbers, and it handles binary numbers. However fs_param_is_string
>> appears to only handle strings. It appears to have not capacity to turn
>> raw binary numbers into strings.
>
> I use result only with hidepid_u32_spec and nobody modifies param->string.
> I do not use internal functions here.
>
> I don’t follow how a raw number can get here ?
I may be wrong but last I looked you can input raw numbers using the new
mount api. I have most of the details paged out at the moment,
but I believe that is why when you set a parameter in the new mount api
it takes a type.
>> So I think we probably need to fix fs_param_is_string to raw binary
>> numbers before we can safely make this change to fs/proc/root.c
>>
>> David am I reading the fs_parser.c code correctly? If I am are you ok
>> with a change like the above?
Eric
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