linux-kernel - [PATCH 3.16 316/366] s390/qdio: fix access to uninitialized qdio

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Message-ID: <lsq.1539530741.151144951@decadent.org.uk>
Date:   Sun, 14 Oct 2018 16:25:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Julian Wiedmann" <jwi@...ux.ibm.com>,
        "Martin Schwidefsky" <schwidefsky@...ibm.com>
Subject: [PATCH 3.16 316/366] s390/qdio: fix access to uninitialized
 qdio_q fields

3.16.60-rc1 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")
Signed-off-by: Julian Wiedmann <jwi@...ux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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
@@ -90,7 +90,7 @@ 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;