This is a note to let you know that I've just added the patch titled
s390/dasd: fix null pointer dereference for ERP requests
to the 5.4-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:
s390-dasd-fix-null-pointer-dereference-for-erp-requests.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6f117cb854a44a79898d844e6ae3fd23bd94e786 Mon Sep 17 00:00:00 2001
From: Stefan Haberland <sth@xxxxxxxxxxxxx>
Date: Mon, 16 Nov 2020 16:23:47 +0100
Subject: s390/dasd: fix null pointer dereference for ERP requests
From: Stefan Haberland <sth@xxxxxxxxxxxxx>
commit 6f117cb854a44a79898d844e6ae3fd23bd94e786 upstream.
When requeueing all requests on the device request queue to the blocklayer
we might get to an ERP (error recovery) request that is a copy of an
original CQR.
Those requests do not have blocklayer request information or a pointer to
the dasd_queue set. When trying to access those data it will lead to a
null pointer dereference in dasd_requeue_all_requests().
Fix by checking if the request is an ERP request that can simply be
ignored. The blocklayer request will be requeued by the original CQR that
is on the device queue right behind the ERP request.
Fixes: 9487cfd3430d ("s390/dasd: fix handling of internal requests")
Cc: <stable@xxxxxxxxxxxxxxx> #4.16
Signed-off-by: Stefan Haberland <sth@xxxxxxxxxxxxx>
Reviewed-by: Jan Hoeppner <hoeppner@xxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/s390/block/dasd.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -2980,6 +2980,12 @@ static int _dasd_requeue_request(struct
if (!block)
return -EINVAL;
+ /*
+ * If the request is an ERP request there is nothing to requeue.
+ * This will be done with the remaining original request.
+ */
+ if (cqr->refers)
+ return 0;
spin_lock_irq(&cqr->dq->lock);
req = (struct request *) cqr->callback_data;
blk_mq_requeue_request(req, false);
Patches currently in stable-queue which might be from sth@xxxxxxxxxxxxx are
queue-5.4/s390-dasd-fix-null-pointer-dereference-for-erp-requests.patch
