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, 59 insertions, 0 deletions

diff --git a/fs/ext2/xattr_security.c b/fs/ext2/xattr_security.c
new file mode 100644
index 000000000..db47b8ab1
--- /dev/null
+++ b/fs/ext2/xattr_security.c
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/ext2/xattr_security.c
+ * Handler for storing security labels as extended attributes.
+ */
+
+#include "ext2.h"
+#include <linux/security.h>
+#include "xattr.h"
+
+static int
+ext2_xattr_security_get(const struct xattr_handler *handler,
+			struct dentry *unused, struct inode *inode,
+			const char *name, void *buffer, size_t size)
+{
+	return ext2_xattr_get(inode, EXT2_XATTR_INDEX_SECURITY, name,
+			      buffer, size);
+}
+
+static int
+ext2_xattr_security_set(const struct xattr_handler *handler,
+			struct mnt_idmap *idmap,
+			struct dentry *unused, struct inode *inode,
+			const char *name, const void *value,
+			size_t size, int flags)
+{
+	return ext2_xattr_set(inode, EXT2_XATTR_INDEX_SECURITY, name,
+			      value, size, flags);
+}
+
+static int ext2_initxattrs(struct inode *inode, const struct xattr *xattr_array,
+			   void *fs_info)
+{
+	const struct xattr *xattr;
+	int err = 0;
+
+	for (xattr = xattr_array; xattr->name != NULL; xattr++) {
+		err = ext2_xattr_set(inode, EXT2_XATTR_INDEX_SECURITY,
+				     xattr->name, xattr->value,
+				     xattr->value_len, 0);
+		if (err < 0)
+			break;
+	}
+	return err;
+}
+
+int
+ext2_init_security(struct inode *inode, struct inode *dir,
+		   const struct qstr *qstr)
+{
+	return security_inode_init_security(inode, dir, qstr,
+					    &ext2_initxattrs, NULL);
+}
+
+const struct xattr_handler ext2_xattr_security_handler = {
+	.prefix	= XATTR_SECURITY_PREFIX,
+	.get	= ext2_xattr_security_get,
+	.set	= ext2_xattr_security_set,
+};