This is a note to let you know that I've just added the patch titled
batman-adv: Fix hang up with small MTU hard-interface
to the 5.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
batman-adv-fix-hang-up-with-small-mtu-hard-interface.patch
and it can be found in the queue-5.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 4daf4c1ceeb35680c4e67270c0bc741a31de7f75
Author: Shigeru Yoshida <syoshida@xxxxxxxxxx>
Date: Sat Aug 20 12:25:16 2022 +0900
batman-adv: Fix hang up with small MTU hard-interface
[ Upstream commit b1cb8a71f1eaec4eb77051590f7f561f25b15e32 ]
The system hangs up when batman-adv soft-interface is created on
hard-interface with small MTU. For example, the following commands
create batman-adv soft-interface on dummy interface with zero MTU:
# ip link add name dummy0 type dummy
# ip link set mtu 0 dev dummy0
# ip link set up dev dummy0
# ip link add name bat0 type batadv
# ip link set dev dummy0 master bat0
These commands cause the system hang up with the following messages:
[ 90.578925][ T6689] batman_adv: bat0: Adding interface: dummy0
[ 90.580884][ T6689] batman_adv: bat0: The MTU of interface dummy0 is too small (0) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1560 would solve the problem.
[ 90.586264][ T6689] batman_adv: bat0: Interface activated: dummy0
[ 90.590061][ T6689] batman_adv: bat0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
[ 90.595517][ T6689] batman_adv: bat0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
[ 90.598499][ T6689] batman_adv: bat0: Forced to purge local tt entries to fit new maximum fragment MTU (-320)
This patch fixes this issue by returning error when enabling
hard-interface with small MTU size.
Fixes: c6c8fea29769 ("net: Add batman-adv meshing protocol")
Signed-off-by: Shigeru Yoshida <syoshida@xxxxxxxxxx>
Signed-off-by: Sven Eckelmann <sven@xxxxxxxxxxxxx>
Signed-off-by: Simon Wunderlich <sw@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index b8f8da7ee3de..41c1ad33d009 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -10,6 +10,7 @@
#include <linux/atomic.h>
#include <linux/byteorder/generic.h>
#include <linux/container_of.h>
+#include <linux/errno.h>
#include <linux/gfp.h>
#include <linux/if.h>
#include <linux/if_arp.h>
@@ -700,6 +701,9 @@ int batadv_hardif_enable_interface(struct batadv_hard_iface *hard_iface,
int max_header_len = batadv_max_header_len();
int ret;
+ if (hard_iface->net_dev->mtu < ETH_MIN_MTU + max_header_len)
+ return -EINVAL;
+
if (hard_iface->if_status != BATADV_IF_NOT_IN_USE)
goto out;
