linux-kernel - [PATCH 4/4] ax.25: Remove the now superfluous sentinel elements from ctl

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Date: Thu, 14 Mar 2024 20:20:44 +0100
From: Joel Granados via B4 Relay <devnull+j.granados.samsung.com@...nel.org>
To: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
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Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
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 coreteam@...filter.org, bridge@...ts.linux.dev, lvs-devel@...r.kernel.org, 
 Joel Granados <j.granados@...sung.com>
Subject: [PATCH 4/4] ax.25: Remove the now superfluous sentinel elements
 from ctl_table array

From: Joel Granados <j.granados@...sung.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/)

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. This did not have any adverse
effects as we still stopped on the sentinel because of its null
procname. But now that we do not have the sentinel element, we are
careful to check ax25_param_table's size.

Signed-off-by: Joel Granados <j.granados@...sung.com>
---
 net/ax25/sysctl_net_ax25.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/ax25/sysctl_net_ax25.c b/net/ax25/sysctl_net_ax25.c
index db66e11e7fe8..2ee375a6a69c 100644
--- a/net/ax25/sysctl_net_ax25.c
+++ b/net/ax25/sysctl_net_ax25.c
@@ -141,8 +141,7 @@ static const struct ctl_table ax25_param_table[] = {
 		.extra2		= &max_ds_timeout
 	},
 #endif
-
-	{ }	/* that's all, folks! */
+/* that's all, folks! */
 };

 int ax25_register_dev_sysctl(ax25_dev *ax25_dev)
@@ -155,7 +154,7 @@ int ax25_register_dev_sysctl(ax25_dev *ax25_dev)
 	if (!table)
 		return -ENOMEM;

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

 	snprintf(path, sizeof(path), "net/ax25/%s", ax25_dev->dev->name);

-- 
2.43.0