[PATCH 5.15 090/106] usb: gadget: f_fs: change ep->status safe in ffs_epfile_io()

Greg Kroah-Hartman
2022-06-20T13:29:53Z

From: Linyu Yuan <quic_linyyuan@quicinc.com>

commit fb1f16d74e263baa4ad11e31e28b68f144aa55ed upstream.

If a task read/write data in blocking mode, it will wait the completion
in ffs_epfile_io(), if function unbind occurs, ffs_func_unbind() will
kfree ffs ep, once the task wake up, it still dereference the ffs ep to
obtain the request status.

Fix it by moving the request status to io_data which is stack-safe.

Cc: <stable@vger.kernel.org> # 5.15
Reported-by: Michael Wu <michael@allwinnertech.com>
Tested-by: Michael Wu <michael@allwinnertech.com>
Reviewed-by: John Keeping <john@metanate.com>
Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
Link: https://lore.kernel.org/r/1654863478-26228-2-git-send-email-quic_linyyuan@quicinc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/gadget/function/f_fs.c | 34 +++++++++++++++++++---------------
1 file changed, 19 insertions(+), 15 deletions(-)

--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -122,8 +122,6 @@ struct ffs_ep {
struct usb_endpoint_descriptor *descs[3];

u8 num;
-
- int status; /* P: epfile->mutex */
};

struct ffs_epfile {
@@ -227,6 +225,9 @@ struct ffs_io_data {
bool use_sg;

struct ffs_data *ffs;
+
+ int status;
+ struct completion done;
};

struct ffs_desc_helper {
@@ -707,12 +708,15 @@ static const struct file_operations ffs_

static void ffs_epfile_io_complete(struct usb_ep *_ep, struct usb_request *req)
{
+ struct ffs_io_data *io_data = req->context;
+
ENTER();
- if (req->context) {
- struct ffs_ep *ep = _ep->driver_data;
- ep->status = req->status ? req->status : req->actual;
- complete(req->context);
- }
+ if (req->status)
+ io_data->status = req->status;
+ else
+ io_data->status = req->actual;
+
+ complete(&io_data->done);
}

static ssize_t ffs_copy_to_iter(void *data, int data_len, struct iov_iter *iter)
@@ -1050,7 +1054,6 @@ static ssize_t ffs_epfile_io(struct file
WARN(1, "%s: data_len == -EINVAL\n", __func__);
ret = -EINVAL;
} else if (!io_data->aio) {
- DECLARE_COMPLETION_ONSTACK(done);
bool interrupted = false;

req = ep->req;
@@ -1066,7 +1069,8 @@ static ssize_t ffs_epfile_io(struct file

io_data->buf = data;

- req->context = &done;
+ init_completion(&io_data->done);
+ req->context = io_data;
req->complete = ffs_epfile_io_complete;

ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
@@ -1075,7 +1079,7 @@ static ssize_t ffs_epfile_io(struct file

spin_unlock_irq(&epfile->ffs->eps_lock);

- if (wait_for_completion_interruptible(&done)) {
+ if (wait_for_completion_interruptible(&io_data->done)) {
/*
* To avoid race condition with ffs_epfile_io_complete,
* dequeue the request first then check
@@ -1083,17 +1087,17 @@ static ssize_t ffs_epfile_io(struct file
* condition with req->complete callback.
*/
usb_ep_dequeue(ep->ep, req);
- wait_for_completion(&done);
- interrupted = ep->status < 0;
+ wait_for_completion(&io_data->done);
+ interrupted = io_data->status < 0;
}

if (interrupted)
ret = -EINTR;
- else if (io_data->read && ep->status > 0)
- ret = __ffs_epfile_read_data(epfile, data, ep->status,
+ else if (io_data->read && io_data->status > 0)
+ ret = __ffs_epfile_read_data(epfile, data, io_data->status,
&io_data->data);
else
- ret = ep->status;
+ ret = io_data->status;
goto error_mutex;
} else if (!(req = usb_ep_alloc_request(ep->ep, GFP_ATOMIC))) {
ret = -ENOMEM;