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, 149 insertions, 0 deletions

diff --git a/io_uring/splice.c b/io_uring/splice.c
new file mode 100644
index 000000000..e81ebbb91
--- /dev/null
+++ b/io_uring/splice.c
@@ -0,0 +1,149 @@
+// 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/splice.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "filetable.h"
+#include "io_uring.h"
+#include "splice.h"
+
+struct io_splice {
+	struct file			*file_out;
+	loff_t				off_out;
+	loff_t				off_in;
+	u64				len;
+	int				splice_fd_in;
+	unsigned int			flags;
+	struct io_rsrc_node		*rsrc_node;
+};
+
+static int __io_splice_prep(struct io_kiocb *req,
+			    const struct io_uring_sqe *sqe)
+{
+	struct io_splice *sp = io_kiocb_to_cmd(req, struct io_splice);
+	unsigned int valid_flags = SPLICE_F_FD_IN_FIXED | SPLICE_F_ALL;
+
+	sp->len = READ_ONCE(sqe->len);
+	sp->flags = READ_ONCE(sqe->splice_flags);
+	if (unlikely(sp->flags & ~valid_flags))
+		return -EINVAL;
+	sp->splice_fd_in = READ_ONCE(sqe->splice_fd_in);
+	sp->rsrc_node = NULL;
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_tee_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	if (READ_ONCE(sqe->splice_off_in) || READ_ONCE(sqe->off))
+		return -EINVAL;
+	return __io_splice_prep(req, sqe);
+}
+
+void io_splice_cleanup(struct io_kiocb *req)
+{
+	struct io_splice *sp = io_kiocb_to_cmd(req, struct io_splice);
+
+	if (sp->rsrc_node)
+		io_put_rsrc_node(req->ctx, sp->rsrc_node);
+}
+
+static struct file *io_splice_get_file(struct io_kiocb *req,
+				       unsigned int issue_flags)
+{
+	struct io_splice *sp = io_kiocb_to_cmd(req, struct io_splice);
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_rsrc_node *node;
+	struct file *file = NULL;
+
+	if (!(sp->flags & SPLICE_F_FD_IN_FIXED))
+		return io_file_get_normal(req, sp->splice_fd_in);
+
+	io_ring_submit_lock(ctx, issue_flags);
+	node = io_rsrc_node_lookup(&ctx->file_table.data, sp->splice_fd_in);
+	if (node) {
+		node->refs++;
+		sp->rsrc_node = node;
+		file = io_slot_file(node);
+		req->flags |= REQ_F_NEED_CLEANUP;
+	}
+	io_ring_submit_unlock(ctx, issue_flags);
+	return file;
+}
+
+int io_tee(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_splice *sp = io_kiocb_to_cmd(req, struct io_splice);
+	struct file *out = sp->file_out;
+	unsigned int flags = sp->flags & ~SPLICE_F_FD_IN_FIXED;
+	struct file *in;
+	ssize_t ret = 0;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	in = io_splice_get_file(req, issue_flags);
+	if (!in) {
+		ret = -EBADF;
+		goto done;
+	}
+
+	if (sp->len)
+		ret = do_tee(in, out, sp->len, flags);
+
+	if (!(sp->flags & SPLICE_F_FD_IN_FIXED))
+		fput(in);
+done:
+	if (ret != sp->len)
+		req_set_fail(req);
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+int io_splice_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_splice *sp = io_kiocb_to_cmd(req, struct io_splice);
+
+	sp->off_in = READ_ONCE(sqe->splice_off_in);
+	sp->off_out = READ_ONCE(sqe->off);
+	return __io_splice_prep(req, sqe);
+}
+
+int io_splice(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_splice *sp = io_kiocb_to_cmd(req, struct io_splice);
+	struct file *out = sp->file_out;
+	unsigned int flags = sp->flags & ~SPLICE_F_FD_IN_FIXED;
+	loff_t *poff_in, *poff_out;
+	struct file *in;
+	ssize_t ret = 0;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	in = io_splice_get_file(req, issue_flags);
+	if (!in) {
+		ret = -EBADF;
+		goto done;
+	}
+
+	poff_in = (sp->off_in == -1) ? NULL : &sp->off_in;
+	poff_out = (sp->off_out == -1) ? NULL : &sp->off_out;
+
+	if (sp->len)
+		ret = do_splice(in, poff_in, out, poff_out, sp->len, flags);
+
+	if (!(sp->flags & SPLICE_F_FD_IN_FIXED))
+		fput(in);
+done:
+	if (ret != sp->len)
+		req_set_fail(req);
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}