mirror of
https://github.com/openwrt/routing.git
synced 2025-12-21 17:04:33 +04:00
30a3bc22c0
If the MTU of one of an attached interface becomes too small to transmit the local translation table then it must be resized to fit inside all fragments (when enabled) or a single packet. But if the MTU becomes too low to transmit even the header + the VLAN specific part then the resizing of the local TT will never succeed. This can for example happen when the usable space is 110 bytes and 11 VLANs are on top of batman-adv. In this case, at least 116 byte would be needed. There will just be an endless spam of batman_adv: batadv0: Forced to purge local tt entries to fit new maximum fragment MTU (110) in the log but the function will never finish. Problem here is that the timeout will be halved all the time and will then stagnate at 0 and therefore never be able to reduce the table even more. There are other scenarios possible with a similar result. The number of BATADV_TT_CLIENT_NOPURGE entries in the local TT can for example be too high to fit inside a packet. Such a scenario can therefore happen also with only a single VLAN + 7 non-purgable addresses - requiring at least 120 bytes. While this should be handled proactively when: * interface with too low MTU is added * VLAN is added * non-purgeable local mac is added * MTU of an attached interface is reduced * fragmentation setting gets disabled (which most likely requires dropping attached interfaces) not all of these scenarios can be prevented because batman-adv is only consuming events without the the possibility to prevent these actions (non-purgable MAC address added, MTU of an attached interface is reduced). It is therefore necessary to also make sure that the code is able to handle also the situations when there were already incompatible system configuration are present. Signed-off-by: Sven Eckelmann <sven@narfation.org>
36 lines
1.4 KiB
Diff
36 lines
1.4 KiB
Diff
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>
|
|
Origin: upstream, https://git.open-mesh.org/batman-adv.git/commit/aeb35331aa9a17f9affd84c1a5b020aeb4a976f4
|
|
|
|
--- a/net/batman-adv/netlink.c
|
|
+++ b/net/batman-adv/netlink.c
|
|
@@ -494,7 +494,10 @@ 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]) {
|