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, 40 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-versatile.c b/drivers/clocksource/timer-versatile.c
new file mode 100644
index 000000000..f5d017b31
--- /dev/null
+++ b/drivers/clocksource/timer-versatile.c
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *
+ * Copyright (C) 2014 ARM Limited
+ */
+
+#include <linux/clocksource.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/sched_clock.h>
+
+#define SYS_24MHZ 0x05c
+
+static void __iomem *versatile_sys_24mhz;
+
+static u64 notrace versatile_sys_24mhz_read(void)
+{
+	return readl(versatile_sys_24mhz);
+}
+
+static int __init versatile_sched_clock_init(struct device_node *node)
+{
+	void __iomem *base = of_iomap(node, 0);
+
+	of_node_clear_flag(node, OF_POPULATED);
+
+	if (!base)
+		return -ENXIO;
+
+	versatile_sys_24mhz = base + SYS_24MHZ;
+
+	sched_clock_register(versatile_sys_24mhz_read, 32, 24000000);
+
+	return 0;
+}
+TIMER_OF_DECLARE(vexpress, "arm,vexpress-sysreg",
+		       versatile_sched_clock_init);
+TIMER_OF_DECLARE(versatile, "arm,versatile-sysreg",
+		       versatile_sched_clock_init);