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, 46 insertions, 0 deletions

diff --git a/fs/nfs/sysctl.c b/fs/nfs/sysctl.c
new file mode 100644
index 000000000..f579df0e8
--- /dev/null
+++ b/fs/nfs/sysctl.c
@@ -0,0 +1,46 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/nfs/sysctl.c
+ *
+ * Sysctl interface to NFS parameters
+ */
+#include <linux/types.h>
+#include <linux/linkage.h>
+#include <linux/ctype.h>
+#include <linux/fs.h>
+#include <linux/sysctl.h>
+#include <linux/module.h>
+#include <linux/nfs_fs.h>
+
+static struct ctl_table_header *nfs_callback_sysctl_table;
+
+static const struct ctl_table nfs_cb_sysctls[] = {
+	{
+		.procname	= "nfs_mountpoint_timeout",
+		.data		= &nfs_mountpoint_expiry_timeout,
+		.maxlen		= sizeof(nfs_mountpoint_expiry_timeout),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_jiffies,
+	},
+	{
+		.procname	= "nfs_congestion_kb",
+		.data		= &nfs_congestion_kb,
+		.maxlen		= sizeof(nfs_congestion_kb),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec,
+	},
+};
+
+int nfs_register_sysctl(void)
+{
+	nfs_callback_sysctl_table = register_sysctl("fs/nfs", nfs_cb_sysctls);
+	if (nfs_callback_sysctl_table == NULL)
+		return -ENOMEM;
+	return 0;
+}
+
+void nfs_unregister_sysctl(void)
+{
+	unregister_sysctl_table(nfs_callback_sysctl_table);
+	nfs_callback_sysctl_table = NULL;
+}