linux-kernel - Re: [PATCH v2 0/9] encode the values directly in the table entry

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Date: Thu, 21 Mar 2024 16:21:43 +0100
From: Joel Granados <j.granados@...sung.com>
To: <wenyang.linux@...mail.com>
CC: "Eric W . Biederman" <ebiederm@...ssion.com>, Luis Chamberlain
	<mcgrof@...nel.org>, Kees Cook <keescook@...omium.org>, Christian Brauner
	<brauner@...nel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/9] encode the values directly in the table entry

On Sat, Mar 09, 2024 at 06:31:17PM +0800, wenyang.linux@...mail.com wrote:
> From: Wen Yang <wenyang.linux@...mail.com>
> 
> The boundary check of multiple modules uses these static variables (such as
> two_five_five, n_65535, ue_int_max, etc), and they are also not changed.
This message is a bit cryptic. I had to do a fair amount of research to
get what you meant here. Having the context in front is OK with me, but
I would add a bit more information so the reader does not have to go to
the code and grep for the variables that you mean. Something like this:
"When using a sysctl proc_handler that requires a boundary check (like
proce_dointvec_minmax) it is common to use a const variable like n_65535
in net/rxrpc/sysctl.c or OTHER EXAMPLES...). This is suboptimal because
YOUR REASONS HERE"


> 
> Eric points out: "by turning .extra1 and .extra2 into longs instead of
> keeping them as pointers and needing constants to be pointed at somewhere
> ... The only people I can see who find a significant benefit by
> consolidating all of the constants into one place are people who know how
> to stomp kernel memory."
I think it would be better to just link to the lore discussion. 

> 
> This patch series achieves direct encoding values in table entries and still
> maintains compatibility with existing extra1/extra2 pointers.
> Afterwards, we can remove these unnecessary static variables progressively and
> also gradually kill the shared const array.
Two things:
1. Please name the const array: sysctl_vals
2. What is missing from this patchset to completely kill sysctl_vals?

> 
> Wen Yang (9):
>   sysctl: support encoding values directly in the table entry
>   kernel/sysctl-test: add some kunit test cases for min/max detection
>   rxrpc: delete these unnecessary static variables n_65535, four,
>     max_500, etc
>   net: ipv6: delete these unnecessary static variables two_five_five and
>     minus_one
>   svcrdma: delete these unnecessary static variables min_ord, max_ord,
>     etc
>   sysctl: delete these unnecessary static variables i_zero and
>     i_one_hundred
>   epoll: delete these unnecessary static variables long_zero and
>     long_max
>   fs: inotify: delete these unnecessary static variables it_zero and
>     it_int_max
>   ucounts: delete these unnecessary static variables ue_zero and
>     ue_int_max
> 
>  fs/eventpoll.c                   |  19 +-
>  fs/notify/inotify/inotify_user.c |  49 +++--
>  include/linux/sysctl.h           | 108 ++++++++++-
>  kernel/sysctl-test.c             | 300 +++++++++++++++++++++++++++++++
>  kernel/sysctl.c                  |  61 +++++--
>  kernel/ucount.c                  |   8 +-
>  lib/test_sysctl.c                |  12 +-
>  net/ipv6/addrconf.c              |  15 +-
>  net/rxrpc/sysctl.c               | 169 ++++++++---------
>  net/sunrpc/xprtrdma/svc_rdma.c   |  21 +--
>  10 files changed, 571 insertions(+), 191 deletions(-)
> 
> Cc: Eric W. Biederman <ebiederm@...ssion.com>
> Cc: Luis Chamberlain <mcgrof@...nel.org>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Joel Granados <j.granados@...sung.com>
> Cc: Christian Brauner <brauner@...nel.org>
> Cc: linux-kernel@...r.kernel.org
> 
> -- 
> 2.25.1
> 

-- 

Joel Granados

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