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, 127 insertions, 0 deletions

diff --git a/net/wireless/of.c b/net/wireless/of.c
new file mode 100644
index 000000000..99acbea3b
--- /dev/null
+++ b/net/wireless/of.c
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: ISC
+/*
+ * Copyright (C) 2017 Rafał Miłecki <rafal@milecki.pl>
+ */
+
+#include <linux/of.h>
+#include <net/cfg80211.h>
+#include "core.h"
+
+static bool wiphy_freq_limits_valid_chan(struct wiphy *wiphy,
+					 struct ieee80211_freq_range *freq_limits,
+					 unsigned int n_freq_limits,
+					 struct ieee80211_channel *chan)
+{
+	u32 bw = MHZ_TO_KHZ(20);
+	int i;
+
+	for (i = 0; i < n_freq_limits; i++) {
+		struct ieee80211_freq_range *limit = &freq_limits[i];
+
+		if (cfg80211_does_bw_fit_range(limit,
+					       MHZ_TO_KHZ(chan->center_freq),
+					       bw))
+			return true;
+	}
+
+	return false;
+}
+
+static void wiphy_freq_limits_apply(struct wiphy *wiphy,
+				    struct ieee80211_freq_range *freq_limits,
+				    unsigned int n_freq_limits)
+{
+	enum nl80211_band band;
+	int i;
+
+	if (WARN_ON(!n_freq_limits))
+		return;
+
+	for (band = 0; band < NUM_NL80211_BANDS; band++) {
+		struct ieee80211_supported_band *sband = wiphy->bands[band];
+
+		if (!sband)
+			continue;
+
+		for (i = 0; i < sband->n_channels; i++) {
+			struct ieee80211_channel *chan = &sband->channels[i];
+
+			if (chan->flags & IEEE80211_CHAN_DISABLED)
+				continue;
+
+			if (!wiphy_freq_limits_valid_chan(wiphy, freq_limits,
+							  n_freq_limits,
+							  chan)) {
+				pr_debug("Disabling freq %d MHz as it's out of OF limits\n",
+					 chan->center_freq);
+				chan->flags |= IEEE80211_CHAN_DISABLED;
+			}
+		}
+	}
+}
+
+void wiphy_read_of_freq_limits(struct wiphy *wiphy)
+{
+	struct device *dev = wiphy_dev(wiphy);
+	struct device_node *np;
+	struct property *prop;
+	struct ieee80211_freq_range *freq_limits;
+	unsigned int n_freq_limits;
+	const __be32 *p;
+	int len, i;
+	int err = 0;
+
+	if (!dev)
+		return;
+	np = dev_of_node(dev);
+	if (!np)
+		return;
+
+	prop = of_find_property(np, "ieee80211-freq-limit", &len);
+	if (!prop)
+		return;
+
+	if (!len || len % sizeof(u32) || len / sizeof(u32) % 2) {
+		dev_err(dev, "ieee80211-freq-limit wrong format");
+		return;
+	}
+	n_freq_limits = len / sizeof(u32) / 2;
+
+	freq_limits = kzalloc_objs(*freq_limits, n_freq_limits);
+	if (!freq_limits) {
+		err = -ENOMEM;
+		goto out_kfree;
+	}
+
+	p = NULL;
+	for (i = 0; i < n_freq_limits; i++) {
+		struct ieee80211_freq_range *limit = &freq_limits[i];
+
+		p = of_prop_next_u32(prop, p, &limit->start_freq_khz);
+		if (!p) {
+			err = -EINVAL;
+			goto out_kfree;
+		}
+
+		p = of_prop_next_u32(prop, p, &limit->end_freq_khz);
+		if (!p) {
+			err = -EINVAL;
+			goto out_kfree;
+		}
+
+		if (!limit->start_freq_khz ||
+		    !limit->end_freq_khz ||
+		    limit->start_freq_khz >= limit->end_freq_khz) {
+			err = -EINVAL;
+			goto out_kfree;
+		}
+	}
+
+	wiphy_freq_limits_apply(wiphy, freq_limits, n_freq_limits);
+
+out_kfree:
+	kfree(freq_limits);
+	if (err)
+		dev_err(dev, "Failed to get limits: %d\n", err);
+}
+EXPORT_SYMBOL(wiphy_read_of_freq_limits);