Re: [PATCH v2 4/4] ax.25: Remove the now superfluous sentinel elements from ctl_table array

From: Joel Granados <j.granados@samsung.com>
To: Kuniyuki Iwashima <kuniyu@amazon.com>
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Subject: Re: [PATCH v2 4/4] ax.25: Remove the now superfluous sentinel elements from ctl_table array
Date: Fri, 12 Apr 2024 16:50:00 +0200	[thread overview]
Message-ID: <20240412145000.4nrf5sufnwjltdl4@joelS2.panther.com> (raw)
In-Reply-To: <20240405222658.3615-1-kuniyu@amazon.com>

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On Fri, Apr 05, 2024 at 03:26:58PM -0700, Kuniyuki Iwashima wrote:
> From: Joel Granados <j.granados@samsung.com>
> Date: Fri, 5 Apr 2024 09:15:31 +0200
> > On Thu, Mar 28, 2024 at 12:49:34PM -0700, Kuniyuki Iwashima wrote:
> > > From: Joel Granados via B4 Relay <devnull+j.granados.samsung.com@kernel.org>
> > > Date: Thu, 28 Mar 2024 16:40:05 +0100
> > > > This commit comes at the tail end of a greater effort to remove the
> > > > empty elements at the end of the ctl_table arrays (sentinels) which will
> > > > reduce the overall build time size of the kernel and run time memory
> > > > bloat by ~64 bytes per sentinel (further information Link :
> > > > https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)
> > > > 
> > > > When we remove the sentinel from ax25_param_table a buffer overflow
> > > > shows its ugly head. The sentinel's data element used to be changed when
> > > > CONFIG_AX25_DAMA_SLAVE was not defined.
> > > 
> > > I think it's better to define the relation explicitly between the
> > > enum and sysctl table by BUILD_BUG_ON() in ax25_register_dev_sysctl()
> > > 
> > >   BUILD_BUG_ON(AX25_MAX_VALUES != ARRAY_SIZE(ax25_param_table));
> > > 
> > > and guard AX25_VALUES_DS_TIMEOUT with #ifdef CONFIG_AX25_DAMA_SLAVE
> > > as done for other enum.
> > 
> > When I remove AX25_VALUES_DS_TIMEOUT from the un-guarded build it
> > complains in net/ax25/ax25_ds_timer.c (ax25_ds_set_timer). Here is the
> > report https://lore.kernel.org/oe-kbuild-all/202404040301.qzKmVQGB-lkp@intel.com/.
> > 
> > How best to address this? Should we just guard the whole function and do
> > nothing when not set? like this:
> 
> It seems fine to me.
> 
> ax25_ds_timeout() checks !ax25_dev->dama.slave_timeout, but it's
> initialised by kzalloc() during dev setup, so it will be a noop.

Just sent v3 with this change.

-- 

Joel Granados

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