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, 98 insertions, 0 deletions

diff --git a/lib/once.c b/lib/once.c
new file mode 100644
index 000000000..d801bfa94
--- /dev/null
+++ b/lib/once.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/once.h>
+#include <linux/random.h>
+#include <linux/module.h>
+
+struct once_work {
+	struct work_struct work;
+	struct static_key_true *key;
+	struct module *module;
+};
+
+static void once_deferred(struct work_struct *w)
+{
+	struct once_work *work;
+
+	work = container_of(w, struct once_work, work);
+	BUG_ON(!static_key_enabled(work->key));
+	static_branch_disable(work->key);
+	module_put(work->module);
+	kfree(work);
+}
+
+static void once_disable_jump(struct static_key_true *key, struct module *mod)
+{
+	struct once_work *w;
+
+	w = kmalloc_obj(*w, GFP_ATOMIC);
+	if (!w)
+		return;
+
+	INIT_WORK(&w->work, once_deferred);
+	w->key = key;
+	w->module = mod;
+	__module_get(mod);
+	schedule_work(&w->work);
+}
+
+static DEFINE_SPINLOCK(once_lock);
+
+bool __do_once_start(bool *done, unsigned long *flags)
+	__acquires(once_lock)
+{
+	spin_lock_irqsave(&once_lock, *flags);
+	if (*done) {
+		spin_unlock_irqrestore(&once_lock, *flags);
+		/* Keep sparse happy by restoring an even lock count on
+		 * this lock. In case we return here, we don't call into
+		 * __do_once_done but return early in the DO_ONCE() macro.
+		 */
+		__acquire(once_lock);
+		return false;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL(__do_once_start);
+
+void __do_once_done(bool *done, struct static_key_true *once_key,
+		    unsigned long *flags, struct module *mod)
+	__releases(once_lock)
+{
+	*done = true;
+	spin_unlock_irqrestore(&once_lock, *flags);
+	once_disable_jump(once_key, mod);
+}
+EXPORT_SYMBOL(__do_once_done);
+
+static DEFINE_MUTEX(once_mutex);
+
+bool __do_once_sleepable_start(bool *done)
+	__acquires(once_mutex)
+{
+	mutex_lock(&once_mutex);
+	if (*done) {
+		mutex_unlock(&once_mutex);
+		/* Keep sparse happy by restoring an even lock count on
+		 * this mutex. In case we return here, we don't call into
+		 * __do_once_done but return early in the DO_ONCE_SLEEPABLE() macro.
+		 */
+		__acquire(once_mutex);
+		return false;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL(__do_once_sleepable_start);
+
+void __do_once_sleepable_done(bool *done, struct static_key_true *once_key,
+			 struct module *mod)
+	__releases(once_mutex)
+{
+	*done = true;
+	mutex_unlock(&once_mutex);
+	static_branch_disable(once_key);
+}
+EXPORT_SYMBOL(__do_once_sleepable_done);