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, 44 insertions, 0 deletions

diff --git a/drivers/video/videomode.c b/drivers/video/videomode.c
new file mode 100644
index 000000000..2ecf80c08
--- /dev/null
+++ b/drivers/video/videomode.c
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * generic display timing functions
+ *
+ * Copyright (c) 2012 Steffen Trumtrar <s.trumtrar@pengutronix.de>, Pengutronix
+ */
+
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <video/display_timing.h>
+#include <video/videomode.h>
+
+void videomode_from_timing(const struct display_timing *dt,
+			  struct videomode *vm)
+{
+	vm->pixelclock = dt->pixelclock.typ;
+	vm->hactive = dt->hactive.typ;
+	vm->hfront_porch = dt->hfront_porch.typ;
+	vm->hback_porch = dt->hback_porch.typ;
+	vm->hsync_len = dt->hsync_len.typ;
+
+	vm->vactive = dt->vactive.typ;
+	vm->vfront_porch = dt->vfront_porch.typ;
+	vm->vback_porch = dt->vback_porch.typ;
+	vm->vsync_len = dt->vsync_len.typ;
+
+	vm->flags = dt->flags;
+}
+EXPORT_SYMBOL_GPL(videomode_from_timing);
+
+int videomode_from_timings(const struct display_timings *disp,
+			  struct videomode *vm, unsigned int index)
+{
+	struct display_timing *dt;
+
+	dt = display_timings_get(disp, index);
+	if (!dt)
+		return -EINVAL;
+
+	videomode_from_timing(dt, vm);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(videomode_from_timings);