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* [PATCH AUTOSEL 4.4 1/3] ax25: NPD bug when detaching AX25 device
@ 2021-12-27 19:06 Sasha Levin
  2021-12-27 19:06 ` [PATCH AUTOSEL 4.4 2/3] phonet/pep: refuse to enable an unbound pipe Sasha Levin
  2021-12-27 19:06 ` [PATCH AUTOSEL 4.4 3/3] platform/x86: apple-gmux: use resource_size() with res Sasha Levin
  0 siblings, 2 replies; 3+ messages in thread
From: Sasha Levin @ 2021-12-27 19:06 UTC (permalink / raw)
  To: linux-kernel, stable
  Cc: Lin Ma, Hanjie Wu, David S . Miller, Sasha Levin, jreuter, kuba,
	linux-hams, netdev

From: Lin Ma <linma@zju.edu.cn>

[ Upstream commit 1ade48d0c27d5da1ccf4b583d8c5fc8b534a3ac8 ]

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@zju.edu.cn>
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/ax25/af_ax25.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c
index 64fede18aa33f..f4c8567e91b38 100644
--- a/net/ax25/af_ax25.c
+++ b/net/ax25/af_ax25.c
@@ -88,8 +88,10 @@ static void ax25_kill_by_device(struct net_device *dev)
 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);
 
-- 
2.34.1


^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2021-12-27 19:08 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-12-27 19:06 [PATCH AUTOSEL 4.4 1/3] ax25: NPD bug when detaching AX25 device Sasha Levin
2021-12-27 19:06 ` [PATCH AUTOSEL 4.4 2/3] phonet/pep: refuse to enable an unbound pipe Sasha Levin
2021-12-27 19:06 ` [PATCH AUTOSEL 4.4 3/3] platform/x86: apple-gmux: use resource_size() with res Sasha Levin

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