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, 83 insertions, 0 deletions

diff --git a/rust/helpers/cpumask.c b/rust/helpers/cpumask.c
new file mode 100644
index 000000000..5deced5b9
--- /dev/null
+++ b/rust/helpers/cpumask.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/cpumask.h>
+
+__rust_helper
+void rust_helper_cpumask_set_cpu(unsigned int cpu, struct cpumask *dstp)
+{
+	cpumask_set_cpu(cpu, dstp);
+}
+
+__rust_helper
+void rust_helper___cpumask_set_cpu(unsigned int cpu, struct cpumask *dstp)
+{
+	__cpumask_set_cpu(cpu, dstp);
+}
+
+__rust_helper
+void rust_helper_cpumask_clear_cpu(int cpu, struct cpumask *dstp)
+{
+	cpumask_clear_cpu(cpu, dstp);
+}
+
+__rust_helper
+void rust_helper___cpumask_clear_cpu(int cpu, struct cpumask *dstp)
+{
+	__cpumask_clear_cpu(cpu, dstp);
+}
+
+__rust_helper
+bool rust_helper_cpumask_test_cpu(int cpu, struct cpumask *srcp)
+{
+	return cpumask_test_cpu(cpu, srcp);
+}
+
+__rust_helper
+void rust_helper_cpumask_setall(struct cpumask *dstp)
+{
+	cpumask_setall(dstp);
+}
+
+__rust_helper
+bool rust_helper_cpumask_empty(struct cpumask *srcp)
+{
+	return cpumask_empty(srcp);
+}
+
+__rust_helper
+bool rust_helper_cpumask_full(struct cpumask *srcp)
+{
+	return cpumask_full(srcp);
+}
+
+__rust_helper
+unsigned int rust_helper_cpumask_weight(struct cpumask *srcp)
+{
+	return cpumask_weight(srcp);
+}
+
+__rust_helper
+void rust_helper_cpumask_copy(struct cpumask *dstp, const struct cpumask *srcp)
+{
+	cpumask_copy(dstp, srcp);
+}
+
+__rust_helper
+bool rust_helper_alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
+{
+	return alloc_cpumask_var(mask, flags);
+}
+
+__rust_helper
+bool rust_helper_zalloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
+{
+	return zalloc_cpumask_var(mask, flags);
+}
+
+#ifndef CONFIG_CPUMASK_OFFSTACK
+__rust_helper
+void rust_helper_free_cpumask_var(cpumask_var_t mask)
+{
+	free_cpumask_var(mask);
+}
+#endif