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/tools/perf/util/evswitch.c b/tools/perf/util/evswitch.c
new file mode 100644
index 000000000..d4c06a3f8
--- /dev/null
+++ b/tools/perf/util/evswitch.c
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (C) 2019, Red Hat Inc, Arnaldo Carvalho de Melo <acme@redhat.com>
+
+#include <errno.h>
+#include "evswitch.h"
+#include "evlist.h"
+
+bool evswitch__discard(struct evswitch *evswitch, struct evsel *evsel)
+{
+	if (evswitch->on && evswitch->discarding) {
+		if (evswitch->on != evsel)
+			return true;
+
+		evswitch->discarding = false;
+
+		if (!evswitch->show_on_off_events)
+			return true;
+
+		return false;
+	}
+
+	if (evswitch->off && !evswitch->discarding) {
+		if (evswitch->off != evsel)
+			return false;
+
+		evswitch->discarding = true;
+
+		if (!evswitch->show_on_off_events)
+			return true;
+	}
+
+	return false;
+}
+
+static int evswitch__fprintf_enoent(FILE *fp, const char *evtype, const char *evname)
+{
+	int printed = fprintf(fp, "ERROR: switch-%s event not found (%s)\n", evtype, evname);
+
+	return printed += fprintf(fp, "HINT:  use 'perf evlist' to see the available event names\n");
+}
+
+int evswitch__init(struct evswitch *evswitch, struct evlist *evlist, FILE *fp)
+{
+	if (evswitch->on_name) {
+		evswitch->on = evlist__find_evsel_by_str(evlist, evswitch->on_name);
+		if (evswitch->on == NULL) {
+			evswitch__fprintf_enoent(fp, "on", evswitch->on_name);
+			return -ENOENT;
+		}
+		evswitch->discarding = true;
+	}
+
+	if (evswitch->off_name) {
+		evswitch->off = evlist__find_evsel_by_str(evlist, evswitch->off_name);
+		if (evswitch->off == NULL) {
+			evswitch__fprintf_enoent(fp, "off", evswitch->off_name);
+			return -ENOENT;
+		}
+	}
+
+	return 0;
+}