[PATCH v5 8/8] ax.25: x.25: Remove the now superfluous sentinel elements from ctl_table array

Joel Granados via B4 Relay
2024-04-26T10:47:11Z

From: Joel Granados <j.granados@samsung.com>

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/)

Avoid a buffer overflow when traversing the ctl_table by ensuring that
AX25_MAX_VALUES is the same as the size of ax25_param_table. This is
done with a BUILD_BUG_ON where ax25_param_table is defined and a
CONFIG_AX25_DAMA_SLAVE guard in the unnamed enum definition as well as
in the ax25_dev_device_up and ax25_ds_set_timer functions.

The overflow happened when the sentinel was removed from
ax25_param_table. The sentinel's data element was changed when
CONFIG_AX25_DAMA_SLAVE was undefined. This had no adverse effects as it
still stopped on the sentinel's null procname but needed to be addressed
once the sentinel was removed.

Signed-off-by: Joel Granados <j.granados@samsung.com>
---
include/net/ax25.h | 2 ++
net/ax25/ax25_dev.c | 3 +++
net/ax25/ax25_ds_timer.c | 4 ++++
net/ax25/sysctl_net_ax25.c | 3 +--
net/x25/sysctl_net_x25.c | 1 -
5 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/include/net/ax25.h b/include/net/ax25.h
index 0d939e5aee4e..eb9cee8252c8 100644
--- a/include/net/ax25.h
+++ b/include/net/ax25.h
@@ -139,7 +139,9 @@ enum {
AX25_VALUES_N2, /* Default N2 value */
AX25_VALUES_PACLEN, /* AX.25 MTU */
AX25_VALUES_PROTOCOL, /* Std AX.25, DAMA Slave, DAMA Master */
+#ifdef CONFIG_AX25_DAMA_SLAVE
AX25_VALUES_DS_TIMEOUT, /* DAMA Slave timeout */
+#endif
AX25_MAX_VALUES /* THIS MUST REMAIN THE LAST ENTRY OF THIS LIST */
};

diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c
index c5462486dbca..af547e185a94 100644
--- a/net/ax25/ax25_dev.c
+++ b/net/ax25/ax25_dev.c
@@ -78,7 +78,10 @@ void ax25_dev_device_up(struct net_device *dev)
ax25_dev->values[AX25_VALUES_N2] = AX25_DEF_N2;
ax25_dev->values[AX25_VALUES_PACLEN] = AX25_DEF_PACLEN;
ax25_dev->values[AX25_VALUES_PROTOCOL] = AX25_DEF_PROTOCOL;
+
+#ifdef CONFIG_AX25_DAMA_SLAVE
ax25_dev->values[AX25_VALUES_DS_TIMEOUT]= AX25_DEF_DS_TIMEOUT;
+#endif

#if defined(CONFIG_AX25_DAMA_SLAVE) || defined(CONFIG_AX25_DAMA_MASTER)
ax25_ds_setup_timer(ax25_dev);
diff --git a/net/ax25/ax25_ds_timer.c b/net/ax25/ax25_ds_timer.c
index c4f8adbf8144..8f385d2a7628 100644
--- a/net/ax25/ax25_ds_timer.c
+++ b/net/ax25/ax25_ds_timer.c
@@ -49,12 +49,16 @@ void ax25_ds_del_timer(ax25_dev *ax25_dev)

void ax25_ds_set_timer(ax25_dev *ax25_dev)
{
+#ifdef CONFIG_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
}

/*
diff --git a/net/ax25/sysctl_net_ax25.c b/net/ax25/sysctl_net_ax25.c
index db66e11e7fe8..4e593d36d311 100644
--- a/net/ax25/sysctl_net_ax25.c
+++ b/net/ax25/sysctl_net_ax25.c
@@ -141,8 +141,6 @@ static const struct ctl_table ax25_param_table[] = {
.extra2 = &max_ds_timeout
},
#endif
-
- { } /* that's all, folks! */
};

int ax25_register_dev_sysctl(ax25_dev *ax25_dev)
@@ -155,6 +153,7 @@ int ax25_register_dev_sysctl(ax25_dev *ax25_dev)
if (!table)
return -ENOMEM;

+ BUILD_BUG_ON(ARRAY_SIZE(ax25_param_table) != AX25_MAX_VALUES);
for (k = 0; k < AX25_MAX_VALUES; k++)
table[k].data = &ax25_dev->values[k];

diff --git a/net/x25/sysctl_net_x25.c b/net/x25/sysctl_net_x25.c
index e9802afa43d0..643f50874dfe 100644
--- a/net/x25/sysctl_net_x25.c
+++ b/net/x25/sysctl_net_x25.c
@@ -71,7 +71,6 @@ static struct ctl_table x25_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec,
},
- { },
};

int __init x25_register_sysctl(void)

--
2.43.0