netdev - Re: [PATCH v2 4/4] ax.25: Remove the now superfluous sentinel elements from ctl

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240405222658.3615-1-kuniyu@amazon.com>
Date: Fri, 5 Apr 2024 15:26:58 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <j.granados@...sung.com>
CC: <Dai.Ngo@...cle.com>, <alex.aring@...il.com>, <alibuda@...ux.alibaba.com>,
	<allison.henderson@...cle.com>, <anna@...nel.org>, <bridge@...ts.linux.dev>,
	<chuck.lever@...cle.com>, <coreteam@...filter.org>, <courmisch@...il.com>,
	<davem@...emloft.net>, <dccp@...r.kernel.org>,
	<devnull+j.granados.samsung.com@...nel.org>, <dhowells@...hat.com>,
	<dsahern@...nel.org>, <edumazet@...gle.com>, <fw@...len.de>,
	<geliang@...nel.org>, <guwen@...ux.alibaba.com>,
	<herbert@...dor.apana.org.au>, <horms@...ge.net.au>, <ja@....bg>,
	<jaka@...ux.ibm.com>, <jlayton@...nel.org>, <jmaloy@...hat.com>,
	<jreuter@...na.de>, <kadlec@...filter.org>, <keescook@...omium.org>,
	<kolga@...app.com>, <kuba@...nel.org>, <kuniyu@...zon.com>,
	<linux-afs@...ts.infradead.org>, <linux-hams@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-nfs@...r.kernel.org>,
	<linux-rdma@...r.kernel.org>, <linux-s390@...r.kernel.org>,
	<linux-sctp@...r.kernel.org>, <linux-wpan@...r.kernel.org>,
	<linux-x25@...r.kernel.org>, <lucien.xin@...il.com>,
	<lvs-devel@...r.kernel.org>, <marc.dionne@...istor.com>,
	<marcelo.leitner@...il.com>, <martineau@...nel.org>, <matttbe@...nel.org>,
	<mcgrof@...nel.org>, <miquel.raynal@...tlin.com>, <mptcp@...ts.linux.dev>,
	<ms@....tdt.de>, <neilb@...e.de>, <netdev@...r.kernel.org>,
	<netfilter-devel@...r.kernel.org>, <pabeni@...hat.com>,
	<pablo@...filter.org>, <ralf@...ux-mips.org>, <razor@...ckwall.org>,
	<rds-devel@....oracle.com>, <roopa@...dia.com>, <stefan@...enfreihafen.org>,
	<steffen.klassert@...unet.com>, <tipc-discussion@...ts.sourceforge.net>,
	<tom@...pey.com>, <tonylu@...ux.alibaba.com>,
	<trond.myklebust@...merspace.com>, <wenjia@...ux.ibm.com>,
	<ying.xue@...driver.com>
Subject: Re: [PATCH v2 4/4] ax.25: Remove the now superfluous sentinel elements from ctl_table array

From: Joel Granados <j.granados@...sung.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@...nel.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.


> 
> ```
> void ax25_ds_set_timer(ax25_dev *ax25_dev)
> {
> #ifdef COFNIG_AX25_DAMA_SLAVE
>         if (ax25_dev == NULL)        ···/* paranoia */
>                 return;
> 
>         ax25_dev->dama.slave_timeout =
>                 msecs_to_jiffies(ax25_dev->values[AX25_VALUES_DS_TIMEOUT]) / 10;
>         mod_timer(&ax25_dev->dama.slave_timer, jiffies + HZ);
> #else
>         return;
> #endif
> }
> 
> ```
> 
> I'm not too familiar with this, so pointing me to the "correct" way to
> handle this would be helpfull.

Also, you will need to guard another use of AX25_VALUES_DS_TIMEOUT in
ax25_dev_device_up().

Thanks!