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, 80 insertions, 0 deletions

diff --git a/fs/jfs/jfs_debug.c b/fs/jfs/jfs_debug.c
new file mode 100644
index 000000000..44b62b3c3
--- /dev/null
+++ b/fs/jfs/jfs_debug.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *   Copyright (C) International Business Machines Corp., 2000-2004
+ *   Portions Copyright (C) Christoph Hellwig, 2001-2002
+ */
+
+#include <linux/fs.h>
+#include <linux/ctype.h>
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/uaccess.h>
+#include "jfs_incore.h"
+#include "jfs_filsys.h"
+#include "jfs_debug.h"
+
+#ifdef PROC_FS_JFS /* see jfs_debug.h */
+
+#ifdef CONFIG_JFS_DEBUG
+static int jfs_loglevel_proc_show(struct seq_file *m, void *v)
+{
+	seq_printf(m, "%d\n", jfsloglevel);
+	return 0;
+}
+
+static int jfs_loglevel_proc_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, jfs_loglevel_proc_show, NULL);
+}
+
+static ssize_t jfs_loglevel_proc_write(struct file *file,
+		const char __user *buffer, size_t count, loff_t *ppos)
+{
+	char c;
+
+	if (get_user(c, buffer))
+		return -EFAULT;
+
+	/* yes, I know this is an ASCIIism.  --hch */
+	if (c < '0' || c > '9')
+		return -EINVAL;
+	jfsloglevel = c - '0';
+	return count;
+}
+
+static const struct proc_ops jfs_loglevel_proc_ops = {
+	.proc_open	= jfs_loglevel_proc_open,
+	.proc_read	= seq_read,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= single_release,
+	.proc_write	= jfs_loglevel_proc_write,
+};
+#endif
+
+void jfs_proc_init(void)
+{
+	struct proc_dir_entry *base;
+
+	base = proc_mkdir("fs/jfs", NULL);
+	if (!base)
+		return;
+
+#ifdef CONFIG_JFS_STATISTICS
+	proc_create_single("lmstats", 0, base, jfs_lmstats_proc_show);
+	proc_create_single("txstats", 0, base, jfs_txstats_proc_show);
+	proc_create_single("xtstat", 0, base, jfs_xtstat_proc_show);
+	proc_create_single("mpstat", 0, base, jfs_mpstat_proc_show);
+#endif
+#ifdef CONFIG_JFS_DEBUG
+	proc_create_single("TxAnchor", 0, base, jfs_txanchor_proc_show);
+	proc_create("loglevel", 0, base, &jfs_loglevel_proc_ops);
+#endif
+}
+
+void jfs_proc_clean(void)
+{
+	remove_proc_subtree("fs/jfs", NULL);
+}
+
+#endif /* PROC_FS_JFS */