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, 188 insertions, 0 deletions

diff --git a/tools/perf/bench/syscall.c b/tools/perf/bench/syscall.c
new file mode 100644
index 000000000..e7dc216f7
--- /dev/null
+++ b/tools/perf/bench/syscall.c
@@ -0,0 +1,188 @@
+/*
+ *
+ * syscall.c
+ *
+ * syscall: Benchmark for system call performance
+ */
+#include "../perf.h"
+#include "../util/util.h"
+#include <subcmd/parse-options.h>
+#include "../builtin.h"
+#include "bench.h"
+
+#include <stdio.h>
+#include <sys/time.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <stdlib.h>
+
+#ifndef __NR_fork
+#define __NR_fork -1
+#endif
+
+static	int loops;
+
+static const struct option options[] = {
+	OPT_INTEGER('l', "loop",	&loops,		"Specify number of loops"),
+	OPT_END()
+};
+
+static const char * const bench_syscall_usage[] = {
+	"perf bench syscall <options>",
+	NULL
+};
+
+static void test_fork(void)
+{
+	pid_t pid = fork();
+
+	if (pid < 0) {
+		fprintf(stderr, "fork failed\n");
+		exit(1);
+	} else if (pid == 0) {
+		exit(0);
+	} else {
+		if (waitpid(pid, NULL, 0) < 0) {
+			fprintf(stderr, "waitpid failed\n");
+			exit(1);
+		}
+	}
+}
+
+static void test_execve(void)
+{
+	const char *pathname = "/bin/true";
+	char *const argv[] = { (char *)pathname, NULL };
+	pid_t pid = fork();
+
+	if (pid < 0) {
+		fprintf(stderr, "fork failed\n");
+		exit(1);
+	} else if (pid == 0) {
+		execve(pathname, argv, NULL);
+		fprintf(stderr, "execve /bin/true failed\n");
+		exit(1);
+	} else {
+		if (waitpid(pid, NULL, 0) < 0) {
+			fprintf(stderr, "waitpid failed\n");
+			exit(1);
+		}
+	}
+}
+
+static int bench_syscall_common(int argc, const char **argv, int syscall)
+{
+	struct timeval start, stop, diff;
+	unsigned long long result_usec = 0;
+	const char *name = NULL;
+	int i;
+
+	switch (syscall) {
+	case __NR_fork:
+	case __NR_execve:
+		/* Limit default loop to 10000 times to save time */
+		loops = 10000;
+		break;
+	default:
+		loops = 10000000;
+		break;
+	}
+
+	/* Options -l and --loops override default above */
+	argc = parse_options(argc, argv, options, bench_syscall_usage, 0);
+
+	gettimeofday(&start, NULL);
+
+	for (i = 0; i < loops; i++) {
+		switch (syscall) {
+		case __NR_getppid:
+			getppid();
+			break;
+		case __NR_getpgid:
+			getpgid(0);
+			break;
+		case __NR_fork:
+			test_fork();
+			break;
+		case __NR_execve:
+			test_execve();
+		default:
+			break;
+		}
+	}
+
+	gettimeofday(&stop, NULL);
+	timersub(&stop, &start, &diff);
+
+	switch (syscall) {
+	case __NR_getppid:
+		name = "getppid()";
+		break;
+	case __NR_getpgid:
+		name = "getpgid()";
+		break;
+	case __NR_fork:
+		name = "fork()";
+		break;
+	case __NR_execve:
+		name = "execve()";
+		break;
+	default:
+		break;
+	}
+
+	switch (bench_format) {
+	case BENCH_FORMAT_DEFAULT:
+		printf("# Executed %'d %s calls\n", loops, name);
+
+		result_usec = diff.tv_sec * 1000000;
+		result_usec += diff.tv_usec;
+
+		printf(" %14s: %lu.%03lu [sec]\n\n", "Total time",
+		       (unsigned long) diff.tv_sec,
+		       (unsigned long) (diff.tv_usec/1000));
+
+		printf(" %14lf usecs/op\n",
+		       (double)result_usec / (double)loops);
+		printf(" %'14d ops/sec\n",
+		       (int)((double)loops /
+			     ((double)result_usec / (double)1000000)));
+		break;
+
+	case BENCH_FORMAT_SIMPLE:
+		printf("%lu.%03lu\n",
+		       (unsigned long) diff.tv_sec,
+		       (unsigned long) (diff.tv_usec / 1000));
+		break;
+
+	default:
+		/* reaching here is something disaster */
+		fprintf(stderr, "Unknown format:%d\n", bench_format);
+		exit(1);
+		break;
+	}
+
+	return 0;
+}
+
+int bench_syscall_basic(int argc, const char **argv)
+{
+	return bench_syscall_common(argc, argv, __NR_getppid);
+}
+
+int bench_syscall_getpgid(int argc, const char **argv)
+{
+	return bench_syscall_common(argc, argv, __NR_getpgid);
+}
+
+int bench_syscall_fork(int argc, const char **argv)
+{
+	return bench_syscall_common(argc, argv, __NR_fork);
+}
+
+int bench_syscall_execve(int argc, const char **argv)
+{
+	return bench_syscall_common(argc, argv, __NR_execve);
+}