dmaengine: fix use-after-free in dma_chan_put() and dma_release_channel()grafted

When dma_device_put() drops the last reference on chan->device->ref,
dma_device_release() runs and may free the dma_device along with its
channels.

dma_chan_put() then still reads chan->device->owner via
dma_chan_to_owner() for the trailing module_put(). KASAN catches it:

	slab-use-after-free in dma_chan_put+0x3e6/0x4c0
	Read of size 8 by task insmod/6319
	Freed by task 6319:
	  kfree+0x225/0x470
	  dma_chan_put+0x395/0x4c0
	  dmaengine_put+0xf8/0x160

Cache the module owner in dma_chan_put() before the put so the trailing
module_put() does not need chan->device.

Fixes: 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct")
Suggested-by: Sashiko <sashiko-bot@kernel.org>
Link: https://sashiko.dev/#/patchset/20260518-dmaengine-kref-fix-v1-1-4d6125048fb7@amd.com
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Shivank Garg <shivankg@amd.com>
Link: https://patch.msgid.link/20260822-dmaengine-kref-fix-v5-3-d4a4ee47d927@amd.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

1 files changed, 65 insertions, 0 deletions

diff --git a/net/wireless/ocb.c b/net/wireless/ocb.c
new file mode 100644
index 000000000..7d2d67f13
--- /dev/null
+++ b/net/wireless/ocb.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * OCB mode implementation
+ *
+ * Copyright: (c) 2014 Czech Technical University in Prague
+ *            (c) 2014 Volkswagen Group Research
+ * Copyright (C) 2022-2023 Intel Corporation
+ * Author:    Rostislav Lisovy <rostislav.lisovy@fel.cvut.cz>
+ * Funded by: Volkswagen Group Research
+ */
+
+#include <linux/ieee80211.h>
+#include <net/cfg80211.h>
+#include "nl80211.h"
+#include "core.h"
+#include "rdev-ops.h"
+
+int cfg80211_join_ocb(struct cfg80211_registered_device *rdev,
+		      struct net_device *dev,
+		      struct ocb_setup *setup)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	int err;
+
+	lockdep_assert_wiphy(wdev->wiphy);
+
+	if (dev->ieee80211_ptr->iftype != NL80211_IFTYPE_OCB)
+		return -EOPNOTSUPP;
+
+	if (!rdev->ops->join_ocb)
+		return -EOPNOTSUPP;
+
+	if (WARN_ON(!setup->chandef.chan))
+		return -EINVAL;
+
+	err = rdev_join_ocb(rdev, dev, setup);
+	if (!err)
+		wdev->u.ocb.chandef = setup->chandef;
+
+	return err;
+}
+
+int cfg80211_leave_ocb(struct cfg80211_registered_device *rdev,
+		       struct net_device *dev)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	int err;
+
+	lockdep_assert_wiphy(wdev->wiphy);
+
+	if (dev->ieee80211_ptr->iftype != NL80211_IFTYPE_OCB)
+		return -EOPNOTSUPP;
+
+	if (!rdev->ops->leave_ocb)
+		return -EOPNOTSUPP;
+
+	if (!wdev->u.ocb.chandef.chan)
+		return -ENOTCONN;
+
+	err = rdev_leave_ocb(rdev, dev);
+	if (!err)
+		memset(&wdev->u.ocb.chandef, 0, sizeof(wdev->u.ocb.chandef));
+
+	return err;
+}