From 60b9aef7f2eb7619c71f5cb2f22498d87bf54a3c Mon Sep 17 00:00:00 2001
From: Harald Freudenberger <freude@linux.ibm.com>
Date: Thu, 14 Oct 2021 09:58:24 +0200
Subject: [PATCH] s390/ap: Fix hanging ioctl caused by orphaned replies
Git-commit: 3826350e6dd435e244eb6e47abad5a47c169ebc2
Patch-mainline: v5.16-rc1
References: stable-5.14.19
commit 3826350e6dd435e244eb6e47abad5a47c169ebc2 upstream.
When a queue is switched to soft offline during heavy load and later
switched to soft online again and now used, it may be that the caller
is blocked forever in the ioctl call.
The failure occurs because there is a pending reply after the queue(s)
have been switched to offline. This orphaned reply is received when
the queue is switched to online and is accidentally counted for the
outstanding replies. So when there was a valid outstanding reply and
this orphaned reply is received it counts as the outstanding one thus
dropping the outstanding counter to 0. Voila, with this counter the
receive function is not called any more and the real outstanding reply
is never received (until another request comes in...) and the ioctl
blocks.
The fix is simple. However, instead of readjusting the counter when an
orphaned reply is detected, I check the queue status for not empty and
compare this to the outstanding counter. So if the queue is not empty
then the counter must not drop to 0 but at least have a value of 1.
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/s390/crypto/ap_queue.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/s390/crypto/ap_queue.c b/drivers/s390/crypto/ap_queue.c
index d70c4d3d0907..26203b88ee17 100644
--- a/drivers/s390/crypto/ap_queue.c
+++ b/drivers/s390/crypto/ap_queue.c
@@ -157,6 +157,8 @@ static struct ap_queue_status ap_sm_recv(struct ap_queue *aq)
switch (status.response_code) {
case AP_RESPONSE_NORMAL:
aq->queue_count = max_t(int, 0, aq->queue_count - 1);
+ if (!status.queue_empty && !aq->queue_count)
+ aq->queue_count++;
if (aq->queue_count > 0)
mod_timer(&aq->timeout,
jiffies + aq->request_timeout);
--
2.26.2