This is a note to let you know that I've just added the patch titled
ax25: NPD bug when detaching AX25 device
to the 4.4-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:
ax25-npd-bug-when-detaching-ax25-device.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1ade48d0c27d5da1ccf4b583d8c5fc8b534a3ac8 Mon Sep 17 00:00:00 2001
From: Lin Ma <linma@xxxxxxxxxx>
Date: Fri, 17 Dec 2021 10:29:41 +0800
Subject: ax25: NPD bug when detaching AX25 device
From: Lin Ma <linma@xxxxxxxxxx>
commit 1ade48d0c27d5da1ccf4b583d8c5fc8b534a3ac8 upstream.
The existing cleanup routine implementation is not well synchronized
with the syscall routine. When a device is detaching, below race could
occur.
static int ax25_sendmsg(...) {
...
lock_sock()
ax25 = sk_to_ax25(sk);
if (ax25->ax25_dev == NULL) // CHECK
...
ax25_queue_xmit(skb, ax25->ax25_dev->dev); // USE
...
}
static void ax25_kill_by_device(...) {
...
if (s->ax25_dev == ax25_dev) {
s->ax25_dev = NULL;
...
}
Other syscall functions like ax25_getsockopt, ax25_getname,
ax25_info_show also suffer from similar races. To fix them, this patch
introduce lock_sock() into ax25_kill_by_device in order to guarantee
that the nullify action in cleanup routine cannot proceed when another
socket request is pending.
Signed-off-by: Hanjie Wu <nagi@xxxxxxxxxx>
Signed-off-by: Lin Ma <linma@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ax25/af_ax25.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -88,8 +88,10 @@ static void ax25_kill_by_device(struct n
again:
ax25_for_each(s, &ax25_list) {
if (s->ax25_dev == ax25_dev) {
- s->ax25_dev = NULL;
spin_unlock_bh(&ax25_list_lock);
+ lock_sock(s->sk);
+ s->ax25_dev = NULL;
+ release_sock(s->sk);
ax25_disconnect(s, ENETUNREACH);
spin_lock_bh(&ax25_list_lock);
Patches currently in stable-queue which might be from linma@xxxxxxxxxx are
queue-4.4/hamradio-improve-the-incomplete-fix-to-avoid-npd.patch
queue-4.4/hamradio-defer-ax25-kfree-after-unregister_netdev.patch
queue-4.4/ax25-npd-bug-when-detaching-ax25-device.patch
