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, 197 insertions, 0 deletions

diff --git a/io_uring/xattr.c b/io_uring/xattr.c
new file mode 100644
index 000000000..5303df3f2
--- /dev/null
+++ b/io_uring/xattr.c
@@ -0,0 +1,197 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/namei.h>
+#include <linux/io_uring.h>
+#include <linux/xattr.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "../fs/internal.h"
+
+#include "io_uring.h"
+#include "xattr.h"
+
+struct io_xattr {
+	struct file			*file;
+	struct kernel_xattr_ctx		ctx;
+	struct delayed_filename		filename;
+};
+
+void io_xattr_cleanup(struct io_kiocb *req)
+{
+	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
+
+	dismiss_delayed_filename(&ix->filename);
+	kfree(ix->ctx.kname);
+	kvfree(ix->ctx.kvalue);
+}
+
+static void io_xattr_finish(struct io_kiocb *req, int ret)
+{
+	req->flags &= ~REQ_F_NEED_CLEANUP;
+
+	io_xattr_cleanup(req);
+	io_req_set_res(req, ret, 0);
+}
+
+static int __io_getxattr_prep(struct io_kiocb *req,
+			      const struct io_uring_sqe *sqe)
+{
+	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
+	const char __user *name;
+	int ret;
+
+	INIT_DELAYED_FILENAME(&ix->filename);
+	ix->ctx.kvalue = NULL;
+	name = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	ix->ctx.value = u64_to_user_ptr(READ_ONCE(sqe->addr2));
+	ix->ctx.size = READ_ONCE(sqe->len);
+	ix->ctx.flags = READ_ONCE(sqe->xattr_flags);
+
+	if (ix->ctx.flags)
+		return -EINVAL;
+
+	ix->ctx.kname = kmalloc_obj(*ix->ctx.kname);
+	if (!ix->ctx.kname)
+		return -ENOMEM;
+
+	ret = import_xattr_name(ix->ctx.kname, name);
+	if (ret) {
+		kfree(ix->ctx.kname);
+		return ret;
+	}
+
+	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_fgetxattr_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	return __io_getxattr_prep(req, sqe);
+}
+
+int io_getxattr_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
+	const char __user *path;
+	int ret;
+
+	if (unlikely(req->flags & REQ_F_FIXED_FILE))
+		return -EBADF;
+
+	ret = __io_getxattr_prep(req, sqe);
+	if (ret)
+		return ret;
+
+	path = u64_to_user_ptr(READ_ONCE(sqe->addr3));
+
+	return delayed_getname(&ix->filename, path);
+}
+
+int io_fgetxattr(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = file_getxattr(req->file, &ix->ctx);
+	io_xattr_finish(req, ret);
+	return IOU_COMPLETE;
+}
+
+int io_getxattr(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
+	CLASS(filename_complete_delayed, name)(&ix->filename);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = filename_getxattr(AT_FDCWD, name, LOOKUP_FOLLOW, &ix->ctx);
+	io_xattr_finish(req, ret);
+	return IOU_COMPLETE;
+}
+
+static int __io_setxattr_prep(struct io_kiocb *req,
+			const struct io_uring_sqe *sqe)
+{
+	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
+	const char __user *name;
+	int ret;
+
+	INIT_DELAYED_FILENAME(&ix->filename);
+	name = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	ix->ctx.cvalue = u64_to_user_ptr(READ_ONCE(sqe->addr2));
+	ix->ctx.kvalue = NULL;
+	ix->ctx.size = READ_ONCE(sqe->len);
+	ix->ctx.flags = READ_ONCE(sqe->xattr_flags);
+
+	ix->ctx.kname = kmalloc_obj(*ix->ctx.kname);
+	if (!ix->ctx.kname)
+		return -ENOMEM;
+
+	ret = setxattr_copy(name, &ix->ctx);
+	if (ret) {
+		kfree(ix->ctx.kname);
+		return ret;
+	}
+
+	req->flags |= REQ_F_NEED_CLEANUP;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_setxattr_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
+	const char __user *path;
+	int ret;
+
+	if (unlikely(req->flags & REQ_F_FIXED_FILE))
+		return -EBADF;
+
+	ret = __io_setxattr_prep(req, sqe);
+	if (ret)
+		return ret;
+
+	path = u64_to_user_ptr(READ_ONCE(sqe->addr3));
+
+	return delayed_getname(&ix->filename, path);
+}
+
+int io_fsetxattr_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	return __io_setxattr_prep(req, sqe);
+}
+
+int io_fsetxattr(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = file_setxattr(req->file, &ix->ctx);
+	io_xattr_finish(req, ret);
+	return IOU_COMPLETE;
+}
+
+int io_setxattr(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_xattr *ix = io_kiocb_to_cmd(req, struct io_xattr);
+	CLASS(filename_complete_delayed, name)(&ix->filename);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = filename_setxattr(AT_FDCWD, name, LOOKUP_FOLLOW, &ix->ctx);
+	io_xattr_finish(req, ret);
+	return IOU_COMPLETE;
+}