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, 114 insertions, 0 deletions

diff --git a/io_uring/sync.c b/io_uring/sync.c
new file mode 100644
index 000000000..ab7fa1cd7
--- /dev/null
+++ b/io_uring/sync.c
@@ -0,0 +1,114 @@
+// 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/fsnotify.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "io_uring.h"
+#include "sync.h"
+
+struct io_sync {
+	struct file			*file;
+	loff_t				len;
+	loff_t				off;
+	int				flags;
+	int				mode;
+};
+
+int io_sfr_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_sync *sync = io_kiocb_to_cmd(req, struct io_sync);
+
+	if (unlikely(sqe->addr || sqe->buf_index || sqe->splice_fd_in))
+		return -EINVAL;
+
+	sync->off = READ_ONCE(sqe->off);
+	sync->len = READ_ONCE(sqe->len);
+	sync->flags = READ_ONCE(sqe->sync_range_flags);
+	req->flags |= REQ_F_FORCE_ASYNC;
+
+	return 0;
+}
+
+int io_sync_file_range(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_sync *sync = io_kiocb_to_cmd(req, struct io_sync);
+	int ret;
+
+	/* sync_file_range always requires a blocking context */
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = sync_file_range(req->file, sync->off, sync->len, sync->flags);
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+int io_fsync_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_sync *sync = io_kiocb_to_cmd(req, struct io_sync);
+
+	if (unlikely(sqe->addr || sqe->buf_index || sqe->splice_fd_in))
+		return -EINVAL;
+
+	sync->flags = READ_ONCE(sqe->fsync_flags);
+	if (unlikely(sync->flags & ~IORING_FSYNC_DATASYNC))
+		return -EINVAL;
+
+	sync->off = READ_ONCE(sqe->off);
+	if (sync->off < 0)
+		return -EINVAL;
+	sync->len = READ_ONCE(sqe->len);
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_fsync(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_sync *sync = io_kiocb_to_cmd(req, struct io_sync);
+	loff_t end = sync->off + sync->len;
+	int ret;
+
+	/* fsync always requires a blocking context */
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = vfs_fsync_range(req->file, sync->off, end > 0 ? end : LLONG_MAX,
+				sync->flags & IORING_FSYNC_DATASYNC);
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}
+
+int io_fallocate_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_sync *sync = io_kiocb_to_cmd(req, struct io_sync);
+
+	if (sqe->buf_index || sqe->rw_flags || sqe->splice_fd_in)
+		return -EINVAL;
+
+	sync->off = READ_ONCE(sqe->off);
+	sync->len = READ_ONCE(sqe->addr);
+	sync->mode = READ_ONCE(sqe->len);
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_fallocate(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_sync *sync = io_kiocb_to_cmd(req, struct io_sync);
+	int ret;
+
+	/* fallocate always requiring blocking context */
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = vfs_fallocate(req->file, sync->mode, sync->off, sync->len);
+	if (ret >= 0)
+		fsnotify_modify(req->file);
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}