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, 62 insertions, 0 deletions

diff --git a/drivers/accessibility/speakup/thread.c b/drivers/accessibility/speakup/thread.c
new file mode 100644
index 000000000..2fc75e60f
--- /dev/null
+++ b/drivers/accessibility/speakup/thread.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kthread.h>
+#include <linux/wait.h>
+
+#include "spk_types.h"
+#include "speakup.h"
+#include "spk_priv.h"
+
+DECLARE_WAIT_QUEUE_HEAD(speakup_event);
+EXPORT_SYMBOL_GPL(speakup_event);
+
+int speakup_thread(void *data)
+{
+	unsigned long flags;
+	int should_break;
+	struct bleep our_sound;
+
+	our_sound.active = 0;
+	our_sound.freq = 0;
+	our_sound.jiffies = 0;
+
+	mutex_lock(&spk_mutex);
+	while (1) {
+		DEFINE_WAIT(wait);
+
+		while (1) {
+			spin_lock_irqsave(&speakup_info.spinlock, flags);
+			our_sound = spk_unprocessed_sound;
+			spk_unprocessed_sound.active = 0;
+			prepare_to_wait(&speakup_event, &wait,
+					TASK_INTERRUPTIBLE);
+			should_break = kthread_should_stop() ||
+				our_sound.active ||
+				(synth && synth->catch_up && synth->alive &&
+					(speakup_info.flushing ||
+					!synth_buffer_empty()));
+			spin_unlock_irqrestore(&speakup_info.spinlock, flags);
+			if (should_break)
+				break;
+			mutex_unlock(&spk_mutex);
+			schedule();
+			mutex_lock(&spk_mutex);
+		}
+		finish_wait(&speakup_event, &wait);
+		if (kthread_should_stop())
+			break;
+
+		if (our_sound.active)
+			kd_mksound(our_sound.freq, our_sound.jiffies);
+		if (synth && synth->catch_up && synth->alive) {
+			/*
+			 * It is up to the callee to take the lock, so that it
+			 * can sleep whenever it likes
+			 */
+			synth->catch_up(synth);
+		}
+
+		speakup_start_ttys();
+	}
+	mutex_unlock(&spk_mutex);
+	return 0;
+}