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, 122 insertions, 0 deletions

diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
new file mode 100644
index 000000000..a4e139dee
--- /dev/null
+++ b/tools/objtool/objtool.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
+ */
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <subcmd/exec-cmd.h>
+#include <subcmd/pager.h>
+#include <linux/kernel.h>
+
+#include <objtool/builtin.h>
+#include <objtool/objtool.h>
+#include <objtool/warn.h>
+
+static struct objtool_file file;
+
+struct objtool_file *objtool_open_read(const char *filename)
+{
+	if (file.elf) {
+		ERROR("won't handle more than one file at a time");
+		return NULL;
+	}
+
+	file.elf = elf_open_read(filename, O_RDWR);
+	if (!file.elf)
+		return NULL;
+
+	hash_init(file.insn_hash);
+	INIT_LIST_HEAD(&file.retpoline_call_list);
+	INIT_LIST_HEAD(&file.return_thunk_list);
+	INIT_LIST_HEAD(&file.static_call_list);
+	INIT_LIST_HEAD(&file.mcount_loc_list);
+	INIT_LIST_HEAD(&file.endbr_list);
+	INIT_LIST_HEAD(&file.call_list);
+	file.ignore_unreachables = opts.no_unreachable;
+	file.hints = false;
+
+	return &file;
+}
+
+int objtool_pv_add(struct objtool_file *f, int idx, struct symbol *func)
+{
+	if (!opts.noinstr)
+		return 0;
+
+	if (!f->pv_ops) {
+		ERROR("paravirt confusion");
+		return -1;
+	}
+
+	/*
+	 * These functions will be patched into native code,
+	 * see paravirt_patch().
+	 */
+	if (!strcmp(func->name, "_paravirt_nop") ||
+	    !strcmp(func->name, "_paravirt_ident_64"))
+		return 0;
+
+	/* already added this function */
+	if (!list_empty(&func->pv_target))
+		return 0;
+
+	list_add(&func->pv_target, &f->pv_ops[idx].targets);
+	f->pv_ops[idx].clean = false;
+	return 0;
+}
+
+char *top_level_dir(const char *file)
+{
+	ssize_t len, self_len, file_len;
+	char self[PATH_MAX], *str;
+	int i;
+
+	len = readlink("/proc/self/exe", self, sizeof(self) - 1);
+	if (len <= 0)
+		return NULL;
+	self[len] = '\0';
+
+	for (i = 0; i < 3; i++) {
+		char *s = strrchr(self, '/');
+		if (!s)
+			return NULL;
+		*s = '\0';
+	}
+
+	self_len = strlen(self);
+	file_len = strlen(file);
+
+	str = malloc(self_len + file_len + 2);
+	if (!str)
+		return NULL;
+
+	memcpy(str, self, self_len);
+	str[self_len] = '/';
+	strcpy(str + self_len + 1, file);
+
+	return str;
+}
+
+int main(int argc, const char **argv)
+{
+	static const char *UNUSED = "OBJTOOL_NOT_IMPLEMENTED";
+
+	if (init_signal_handler())
+		return -1;
+
+	/* libsubcmd init */
+	exec_cmd_init("objtool", UNUSED, UNUSED, UNUSED);
+	pager_init(UNUSED);
+
+	if (argc > 1 && !strcmp(argv[1], "klp")) {
+		argc--;
+		argv++;
+		return cmd_klp(argc, argv);
+	}
+
+	return objtool_run(argc, argv);
+}