From: Joel Granados <j.granados@xxxxxxxxxxx> 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@xxxxxxxxxx> > > 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@xxxxxxxxxxxxxxxxxxxxxx/) > > > > > > 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@xxxxxxxxx/. > > 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!
