linux-kernel - [PATCH 4.9 20/87] s390/qdio: fix access to uninitialized qdio

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Message-Id: <20180521210422.154652994@linuxfoundation.org>
Date:   Mon, 21 May 2018 23:10:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Julian Wiedmann <jwi@...ux.ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: [PATCH 4.9 20/87] s390/qdio: fix access to uninitialized qdio_q fields

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Julian Wiedmann <jwi@...ux.ibm.com>

commit e521813468f786271a87e78e8644243bead48fad upstream.

Ever since CQ/QAOB support was added, calling qdio_free() straight after
qdio_alloc() results in qdio_release_memory() accessing uninitialized
memory (ie. q->u.out.use_cq and q->u.out.aobs). Followed by a
kmem_cache_free() on the random AOB addresses.

For older kernels that don't have 6e30c549f6ca, the same applies if
qdio_establish() fails in the DEV_STATE_ONLINE check.

While initializing q->u.out.use_cq would be enough to fix this
particular bug, the more future-proof change is to just zero-alloc the
whole struct.

Fixes: 104ea556ee7f ("qdio: support asynchronous delivery of storage blocks")
Cc: <stable@...r.kernel.org> #v3.2+
Signed-off-by: Julian Wiedmann <jwi@...ux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/s390/cio/qdio_setup.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/s390/cio/qdio_setup.c
+++ b/drivers/s390/cio/qdio_setup.c
@@ -140,7 +140,7 @@ static int __qdio_allocate_qs(struct qdi
 	int i;

 	for (i = 0; i < nr_queues; i++) {
-		q = kmem_cache_alloc(qdio_q_cache, GFP_KERNEL);
+		q = kmem_cache_zalloc(qdio_q_cache, GFP_KERNEL);
 		if (!q)
 			return -ENOMEM;