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, 146 insertions, 0 deletions

diff --git a/net/ceph/auth_none.c b/net/ceph/auth_none.c
new file mode 100644
index 000000000..99e1f3e10
--- /dev/null
+++ b/net/ceph/auth_none.c
@@ -0,0 +1,146 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/ceph/ceph_debug.h>
+
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/random.h>
+#include <linux/slab.h>
+
+#include <linux/ceph/decode.h>
+#include <linux/ceph/auth.h>
+
+#include "auth_none.h"
+
+static void reset(struct ceph_auth_client *ac)
+{
+	struct ceph_auth_none_info *xi = ac->private;
+
+	xi->starting = true;
+}
+
+static void destroy(struct ceph_auth_client *ac)
+{
+	kfree(ac->private);
+	ac->private = NULL;
+}
+
+static int is_authenticated(struct ceph_auth_client *ac)
+{
+	struct ceph_auth_none_info *xi = ac->private;
+
+	return !xi->starting;
+}
+
+static int should_authenticate(struct ceph_auth_client *ac)
+{
+	struct ceph_auth_none_info *xi = ac->private;
+
+	return xi->starting;
+}
+
+static int ceph_auth_none_build_authorizer(struct ceph_auth_client *ac,
+					   struct ceph_none_authorizer *au)
+{
+	void *p = au->buf;
+	void *const end = p + sizeof(au->buf);
+	int ret;
+
+	ceph_encode_8_safe(&p, end, 1, e_range);
+	ret = ceph_auth_entity_name_encode(ac->name, &p, end);
+	if (ret < 0)
+		return ret;
+
+	ceph_encode_64_safe(&p, end, ac->global_id, e_range);
+	au->buf_len = p - (void *)au->buf;
+	dout("%s built authorizer len %d\n", __func__, au->buf_len);
+	return 0;
+
+e_range:
+	return -ERANGE;
+}
+
+static int build_request(struct ceph_auth_client *ac, void *buf, void *end)
+{
+	return 0;
+}
+
+/*
+ * the generic auth code decode the global_id, and we carry no actual
+ * authenticate state, so nothing happens here.
+ */
+static int handle_reply(struct ceph_auth_client *ac, u64 global_id,
+			void *buf, void *end, u8 *session_key,
+			int *session_key_len, u8 *con_secret,
+			int *con_secret_len)
+{
+	struct ceph_auth_none_info *xi = ac->private;
+
+	xi->starting = false;
+	ceph_auth_set_global_id(ac, global_id);
+	return 0;
+}
+
+static void ceph_auth_none_destroy_authorizer(struct ceph_authorizer *a)
+{
+	kfree(a);
+}
+
+/*
+ * build an 'authorizer' with our entity_name and global_id.  it is
+ * identical for all services we connect to.
+ */
+static int ceph_auth_none_create_authorizer(
+	struct ceph_auth_client *ac, int peer_type,
+	struct ceph_auth_handshake *auth)
+{
+	struct ceph_none_authorizer *au;
+	int ret;
+
+	au = kmalloc_obj(*au, GFP_NOFS);
+	if (!au)
+		return -ENOMEM;
+
+	au->base.destroy = ceph_auth_none_destroy_authorizer;
+
+	ret = ceph_auth_none_build_authorizer(ac, au);
+	if (ret) {
+		kfree(au);
+		return ret;
+	}
+
+	auth->authorizer = (struct ceph_authorizer *) au;
+	auth->authorizer_buf = au->buf;
+	auth->authorizer_buf_len = au->buf_len;
+	auth->authorizer_reply_buf = NULL;
+	auth->authorizer_reply_buf_len = 0;
+
+	return 0;
+}
+
+static const struct ceph_auth_client_ops ceph_auth_none_ops = {
+	.reset = reset,
+	.destroy = destroy,
+	.is_authenticated = is_authenticated,
+	.should_authenticate = should_authenticate,
+	.build_request = build_request,
+	.handle_reply = handle_reply,
+	.create_authorizer = ceph_auth_none_create_authorizer,
+};
+
+int ceph_auth_none_init(struct ceph_auth_client *ac)
+{
+	struct ceph_auth_none_info *xi;
+
+	dout("ceph_auth_none_init %p\n", ac);
+	xi = kzalloc_obj(*xi, GFP_NOFS);
+	if (!xi)
+		return -ENOMEM;
+
+	xi->starting = true;
+
+	ac->protocol = CEPH_AUTH_NONE;
+	ac->private = xi;
+	ac->ops = &ceph_auth_none_ops;
+	return 0;
+}