batman-adv: Fix lock assert after fragmentation change

The automatic recalculation of the maximum allowed MTU is usually triggered by code sections which are already rtnl lock protected by callers outside of batman-adv. But when the fragmentation setting is changed via batman-adv's own batadv genl family, then the rtnl lock is not yet taken. But dev_set_mtu requires that the caller holds the rtnl lock because it uses netdevice notifiers. And this code will then fail the check for this lock: RTNL: assertion failed at net/core/dev.c (1953) Fixes: c738e47 ("batman-adv: Merge bugfixes from 2023.2") Signed-off-by: Sven Eckelmann <[email protected]>
openwrt · Aug 22, 2023 · 78ac6ee · 78ac6ee
1 parent c738e47
commit 78ac6ee
Show file tree

Hide file tree

Showing 2 changed files with 36 additions and 1 deletion.
diff --git a/batman-adv/Makefile b/batman-adv/Makefile
@@ -4,7 +4,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=batman-adv
 PKG_VERSION:=2023.1
-PKG_RELEASE:=3
+PKG_RELEASE:=4
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
 PKG_SOURCE_URL:=https://downloads.open-mesh.org/batman/releases/batman-adv-$(PKG_VERSION)

diff --git a/batman-adv/patches/0010-batman-adv-Hold-rtnl-lock-during-MTU-update-via-netl.patch b/batman-adv/patches/0010-batman-adv-Hold-rtnl-lock-during-MTU-update-via-netl.patch
@@ -0,0 +1,35 @@
+From: Sven Eckelmann <[email protected]>
+Date: Mon, 21 Aug 2023 21:48:48 +0200
+Subject: batman-adv: Hold rtnl lock during MTU update via netlink
+
+The automatic recalculation of the maximum allowed MTU is usually triggered
+by code sections which are already rtnl lock protected by callers outside
+of batman-adv. But when the fragmentation setting is changed via
+batman-adv's own batadv genl family, then the rtnl lock is not yet taken.
+
+But dev_set_mtu requires that the caller holds the rtnl lock because it
+uses netdevice notifiers. And this code will then fail the check for this
+lock:
+
+  RTNL: assertion failed at net/core/dev.c (1953)
+
+Cc: [email protected]
+Reported-by: [email protected]
+Fixes: 27c4d7c1c7fa ("batman-adv: Trigger events for auto adjusted MTU")
+Reviewed-by: Simon Horman <[email protected]>
+Signed-off-by: Sven Eckelmann <[email protected]>
+Origin: upstream, https://git.open-mesh.org/batman-adv.git/commit/aeb35331aa9a17f9affd84c1a5b020aeb4a976f4
+
+--- a/net/batman-adv/netlink.c
++++ b/net/batman-adv/netlink.c
+@@ -495,7 +495,10 @@ static int batadv_netlink_set_mesh(struc
+ 		attr = info->attrs[BATADV_ATTR_FRAGMENTATION_ENABLED];
+
+ 		atomic_set(&bat_priv->fragmentation, !!nla_get_u8(attr));
++
++		rtnl_lock();
+ 		batadv_update_min_mtu(bat_priv->soft_iface);
++		rtnl_unlock();
+ 	}
+
+ 	if (info->attrs[BATADV_ATTR_GW_BANDWIDTH_DOWN]) {