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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: e7ee4c55de ("batman-adv: update to version 2023.2")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
This commit is contained in:
Sven Eckelmann 2023-08-22 18:26:35 +02:00
parent 167d93cc32
commit 364379c056
2 changed files with 35 additions and 1 deletions
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2
batman-adv/Makefile
View File

@ -4,7 +4,7 @@ include $(TOPDIR)/rules.mk
PKG_NAME:=batman-adv
PKG_VERSION:=2023.2
PKG_RELEASE:=1
PKG_RELEASE:=2
PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.gz
PKG_SOURCE_URL:=https://downloads.open-mesh.org/batman/releases/batman-adv-$(PKG_VERSION)

34
batman-adv/patches/0003-batman-adv-Hold-rtnl-lock-during-MTU-update-via-netl.patch Normal file
View File

@ -0,0 +1,34 @@
From: Sven Eckelmann <sven@narfation.org>
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: stable@vger.kernel.org
Reported-by: syzbot+f8812454d9b3ac00d282@syzkaller.appspotmail.com
Fixes: 27c4d7c1c7fa ("batman-adv: Trigger events for auto adjusted MTU")
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
--- 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]) {