[PATCH v3 0/2] usb: f_fs: safe operation in ffs_epfile_io()

[PATCH v3 0/2] usb: f_fs: safe operation in ffs_epfile_io()

[Linyu Yuan]

Fix two possible issue in ffs_epfile_io() when operation at blocking mode.

v1: https://lore.kernel.org/linux-usb/1653989775-14267-1-git-send-email-quic_linyyuan@quicinc.com/
v2: correct interrupted variable according comment from John Keeping
v3: (v2: https://lore.kernel.org/linux-usb/1654006119-23869-1-git-send-email-quic_linyyuan@quicinc.com/)
    add Revived-by from John keeping,
    after offline discussion, add Reported-by from Michael Wu

Linyu Yuan (2):
  usb: gadget: f_fs: change ep->status safe in ffs_epfile_io()
  usb: gadget: f_fs: change ep->ep safe in ffs_epfile_io()

 drivers/usb/gadget/function/f_fs.c | 38 +++++++++++++++++++++++---------------
 1 file changed, 23 insertions(+), 15 deletions(-)

-- 
2.7.4

[PATCH v3 1/2] usb: gadget: f_fs: change ep->status safe in ffs_epfile_io()

[Linyu Yuan]

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.

Reported-by: Michael Wu <michael@allwinnertech.com>
Reviewed-by: John Keeping <john@metanate.com>
Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
---
v2: correct interrupted assignment
v3: add Reviewed-by and Reported-by

 drivers/usb/gadget/function/f_fs.c | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 4585ee3..d4d8940 100644
--- 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 +708,12 @@ static const struct file_operations ffs_ep0_operations = {
 
 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);
-	}
+
+	io_data->status = req->status ? req->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 +1051,6 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 		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 +1066,8 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 
 		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 +1076,7 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 
 		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 +1084,18 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 			 * 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;
-- 
2.7.4

[PATCH v3 2/2] usb: gadget: f_fs: change ep->ep safe in ffs_epfile_io()

[Linyu Yuan]

In ffs_epfile_io(), when read/write data in blocking mode, it will wait
the completion in interruptible mode, if task receive a signal, it will
terminate the wait, at same time, if function unbind occurs,
ffs_func_unbind() will kfree all eps, ffs_epfile_io() still try to
dequeue request by dereferencing ep which may become invalid.

Fix it by add ep spinlock and will not dereference ep if it is not valid.

Reported-by: Michael Wu <michael@allwinnertech.com>
Reviewed-by: John Keeping <john@metanate.com>
Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
---
v2: add Reviewed-by from John keeping
v3: add Reported-by from Michael Wu

 drivers/usb/gadget/function/f_fs.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index d4d8940..9bf9287 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -1077,6 +1077,11 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 		spin_unlock_irq(&epfile->ffs->eps_lock);
 
 		if (wait_for_completion_interruptible(&io_data->done)) {
+			spin_lock_irq(&epfile->ffs->eps_lock);
+			if (epfile->ep != ep) {
+				ret = -ESHUTDOWN;
+				goto error_lock;
+			}
 			/*
 			 * To avoid race condition with ffs_epfile_io_complete,
 			 * dequeue the request first then check
@@ -1084,6 +1089,7 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 			 * condition with req->complete callback.
 			 */
 			usb_ep_dequeue(ep->ep, req);
+			spin_unlock_irq(&epfile->ffs->eps_lock);
 			wait_for_completion(&io_data->done);
 			interrupted = io_data->status < 0;
 		}
-- 
2.7.4

Re: [PATCH v3 2/2] usb: gadget: f_fs: change ep->ep safe in ffs_epfile_io()

[Michael Wu]

On 6/1/2022 12:15 PM, Linyu Yuan wrote:
> In ffs_epfile_io(), when read/write data in blocking mode, it will wait
> the completion in interruptible mode, if task receive a signal, it will
> terminate the wait, at same time, if function unbind occurs,
> ffs_func_unbind() will kfree all eps, ffs_epfile_io() still try to
> dequeue request by dereferencing ep which may become invalid.
> 
> Fix it by add ep spinlock and will not dereference ep if it is not valid.
> 
> Reported-by: Michael Wu <michael@allwinnertech.com>
> Reviewed-by: John Keeping <john@metanate.com>
> Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
> ---
> v2: add Reviewed-by from John keeping
> v3: add Reported-by from Michael Wu
> 
>   drivers/usb/gadget/function/f_fs.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> index d4d8940..9bf9287 100644
> --- a/drivers/usb/gadget/function/f_fs.c
> +++ b/drivers/usb/gadget/function/f_fs.c
> @@ -1077,6 +1077,11 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
>   		spin_unlock_irq(&epfile->ffs->eps_lock);
>   
>   		if (wait_for_completion_interruptible(&io_data->done)) {
> +			spin_lock_irq(&epfile->ffs->eps_lock);
> +			if (epfile->ep != ep) {
> +				ret = -ESHUTDOWN;
> +				goto error_lock;
> +			}
>   			/*
>   			 * To avoid race condition with ffs_epfile_io_complete,
>   			 * dequeue the request first then check
> @@ -1084,6 +1089,7 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
>   			 * condition with req->complete callback.
>   			 */
>   			usb_ep_dequeue(ep->ep, req);
> +			spin_unlock_irq(&epfile->ffs->eps_lock);
>   			wait_for_completion(&io_data->done);
>   			interrupted = io_data->status < 0;
>   		}

Tested-by: Michael Wu <michael@allwinnertech.com>

I've tested Linyu's patches [PATCH v3 1/2] [PATCH v3 2/2]. I believe it 
fixes the bug I reported.

What's more, John's solution [1] also works in my tests. It looks 
simpler. I'm not sure if it's as complete as Linyu's solution.


[1] https://lore.kernel.org/linux-usb/YpUJkxWBNuZiW7Xk@donbot/


-- 
Regards,
Michael Wu

Re: [PATCH v3 2/2] usb: gadget: f_fs: change ep->ep safe in ffs_epfile_io()

[John Keeping]

On Thu, Jun 02, 2022 at 06:39:30PM +0800, Michael Wu wrote:
> On 6/1/2022 12:15 PM, Linyu Yuan wrote:
> > In ffs_epfile_io(), when read/write data in blocking mode, it will wait
> > the completion in interruptible mode, if task receive a signal, it will
> > terminate the wait, at same time, if function unbind occurs,
> > ffs_func_unbind() will kfree all eps, ffs_epfile_io() still try to
> > dequeue request by dereferencing ep which may become invalid.
> > 
> > Fix it by add ep spinlock and will not dereference ep if it is not valid.
> > 
> > Reported-by: Michael Wu <michael@allwinnertech.com>
> > Reviewed-by: John Keeping <john@metanate.com>
> > Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>
> > ---
> > v2: add Reviewed-by from John keeping
> > v3: add Reported-by from Michael Wu
> > 
> >   drivers/usb/gadget/function/f_fs.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> > index d4d8940..9bf9287 100644
> > --- a/drivers/usb/gadget/function/f_fs.c
> > +++ b/drivers/usb/gadget/function/f_fs.c
> > @@ -1077,6 +1077,11 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
> >   		spin_unlock_irq(&epfile->ffs->eps_lock);
> >   		if (wait_for_completion_interruptible(&io_data->done)) {
> > +			spin_lock_irq(&epfile->ffs->eps_lock);
> > +			if (epfile->ep != ep) {
> > +				ret = -ESHUTDOWN;
> > +				goto error_lock;
> > +			}
> >   			/*
> >   			 * To avoid race condition with ffs_epfile_io_complete,
> >   			 * dequeue the request first then check
> > @@ -1084,6 +1089,7 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
> >   			 * condition with req->complete callback.
> >   			 */
> >   			usb_ep_dequeue(ep->ep, req);
> > +			spin_unlock_irq(&epfile->ffs->eps_lock);
> >   			wait_for_completion(&io_data->done);
> >   			interrupted = io_data->status < 0;
> >   		}
> 
> Tested-by: Michael Wu <michael@allwinnertech.com>
> 
> I've tested Linyu's patches [PATCH v3 1/2] [PATCH v3 2/2]. I believe it
> fixes the bug I reported.
> 
> What's more, John's solution [1] also works in my tests. It looks simpler.
> I'm not sure if it's as complete as Linyu's solution.

It's not as comprehensive, let's focus on this thread.

> [1] https://lore.kernel.org/linux-usb/YpUJkxWBNuZiW7Xk@donbot/

Re: [PATCH v3 2/2] usb: gadget: f_fs: change ep->ep safe in ffs_epfile_io()

[Michael Wu]

On 6/2/2022 9:06 PM, John Keeping wrote:
> On Thu, Jun 02, 2022 at 06:39:30PM +0800, Michael Wu wrote:
>> Tested-by: Michael Wu <michael@allwinnertech.com>
>>
>> I've tested Linyu's patches [PATCH v3 1/2] [PATCH v3 2/2]. I believe it
>> fixes the bug I reported.
>>
>> What's more, John's solution [1] also works in my tests. It looks simpler.
>> I'm not sure if it's as complete as Linyu's solution.
> 
> It's not as comprehensive, let's focus on this thread.
> 

No problem. Thank you.

-- 
Regards,
Michael Wu