[PATCH v2] can: mcba_usb: Fix memory leak when cancelling urb

[PATCH v2] can: mcba_usb: Fix memory leak when cancelling urb

[Bui Quang Minh]

In mcba_usb_read_bulk_callback(), when we don't resubmit or fails to
resubmit the urb, we need to deallocate the transfer buffer that is
allocated in mcba_usb_start().

Reported-by: syzbot+57281c762a3922e14dfe@syzkaller.appspotmail.com
Signed-off-by: Bui Quang Minh <minhquangbui99@gmail.com>
---
v1: add memory leak fix when not resubmitting urb
v2: add memory leak fix when failing to resubmit urb

 drivers/net/can/usb/mcba_usb.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/net/can/usb/mcba_usb.c b/drivers/net/can/usb/mcba_usb.c
index df54eb7d4b36..30236e640116 100644
--- a/drivers/net/can/usb/mcba_usb.c
+++ b/drivers/net/can/usb/mcba_usb.c
@@ -584,6 +584,8 @@ static void mcba_usb_read_bulk_callback(struct urb *urb)
 	case -EPIPE:
 	case -EPROTO:
 	case -ESHUTDOWN:
+		usb_free_coherent(urb->dev, urb->transfer_buffer_length,
+				  urb->transfer_buffer, urb->transfer_dma);
 		return;
 
 	default:
@@ -615,11 +617,14 @@ static void mcba_usb_read_bulk_callback(struct urb *urb)
 
 	retval = usb_submit_urb(urb, GFP_ATOMIC);
 
-	if (retval == -ENODEV)
-		netif_device_detach(netdev);
-	else if (retval)
+	if (retval < 0) {
 		netdev_err(netdev, "failed resubmitting read bulk urb: %d\n",
 			   retval);
+		usb_free_coherent(urb->dev, urb->transfer_buffer_length,
+				  urb->transfer_buffer, urb->transfer_dma);
+		if (retval == -ENODEV)
+			netif_device_detach(netdev);
+	}
 }
 
 /* Start USB device */
-- 
2.17.1

Re: [PATCH v2] can: mcba_usb: Fix memory leak when cancelling urb

[Oliver Neukum]

Am Montag, den 11.01.2021, 10:49 +0000 schrieb Bui Quang Minh:
> In mcba_usb_read_bulk_callback(), when we don't resubmit or fails to
> resubmit the urb, we need to deallocate the transfer buffer that is
> allocated in mcba_usb_start().
> 
> Reported-by: syzbot+57281c762a3922e14dfe@syzkaller.appspotmail.com
> Signed-off-by: Bui Quang Minh <minhquangbui99@gmail.com>
> ---
> v1: add memory leak fix when not resubmitting urb
> v2: add memory leak fix when failing to resubmit urb
> 
>  drivers/net/can/usb/mcba_usb.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/can/usb/mcba_usb.c b/drivers/net/can/usb/mcba_usb.c
> index df54eb7d4b36..30236e640116 100644
> --- a/drivers/net/can/usb/mcba_usb.c
> +++ b/drivers/net/can/usb/mcba_usb.c
> @@ -584,6 +584,8 @@ static void mcba_usb_read_bulk_callback(struct urb *urb)
>  	case -EPIPE:
>  	case -EPROTO:
>  	case -ESHUTDOWN:
> +		usb_free_coherent(urb->dev, urb->transfer_buffer_length,
> +				  urb->transfer_buffer, urb->transfer_dma);
>  		return;
>  

Can you call usb_free_coherent() in what can be hard IRQ context?

	Regards
		Oliver

Re: [PATCH v2] can: mcba_usb: Fix memory leak when cancelling urb

[Bui Quang Minh]

On Mon, Jan 11, 2021 at 01:00:31PM +0100, Oliver Neukum wrote:
> Am Montag, den 11.01.2021, 10:49 +0000 schrieb Bui Quang Minh:
> > In mcba_usb_read_bulk_callback(), when we don't resubmit or fails to
> > resubmit the urb, we need to deallocate the transfer buffer that is
> > allocated in mcba_usb_start().
> > 
> > Reported-by: syzbot+57281c762a3922e14dfe@syzkaller.appspotmail.com
> > Signed-off-by: Bui Quang Minh <minhquangbui99@gmail.com>
> > ---
> > v1: add memory leak fix when not resubmitting urb
> > v2: add memory leak fix when failing to resubmit urb
> > 
> >  drivers/net/can/usb/mcba_usb.c | 11 ++++++++---
> >  1 file changed, 8 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/net/can/usb/mcba_usb.c b/drivers/net/can/usb/mcba_usb.c
> > index df54eb7d4b36..30236e640116 100644
> > --- a/drivers/net/can/usb/mcba_usb.c
> > +++ b/drivers/net/can/usb/mcba_usb.c
> > @@ -584,6 +584,8 @@ static void mcba_usb_read_bulk_callback(struct urb *urb)
> >  	case -EPIPE:
> >  	case -EPROTO:
> >  	case -ESHUTDOWN:
> > +		usb_free_coherent(urb->dev, urb->transfer_buffer_length,
> > +				  urb->transfer_buffer, urb->transfer_dma);
> >  		return;
> >  
> 
> Can you call usb_free_coherent() in what can be hard IRQ context?

You are right, I digged in the code and saw some comments that on some
architectures, usb_free_coherent() cannot be called in hard IRQ context.
I see the usb_free_coherent() is called in write_bulk_callback too. I will
send a patch that uses usb_anchor to keep track of these urbs and cleanup 
the transfer buffer later in disconnect().

Thank you for your review,
Quang Minh.

Re: [PATCH v2] can: mcba_usb: Fix memory leak when cancelling urb

[Minh Bùi Quang]

On Mon, Jan 11, 2021 at 9:31 PM Bui Quang Minh <minhquangbui99@gmail.com> wrote:
>
> On Mon, Jan 11, 2021 at 01:00:31PM +0100, Oliver Neukum wrote:
> > Am Montag, den 11.01.2021, 10:49 +0000 schrieb Bui Quang Minh:
> > > In mcba_usb_read_bulk_callback(), when we don't resubmit or fails to
> > > resubmit the urb, we need to deallocate the transfer buffer that is
> > > allocated in mcba_usb_start().
> > >
> > > Reported-by: syzbot+57281c762a3922e14dfe@syzkaller.appspotmail.com
> > > Signed-off-by: Bui Quang Minh <minhquangbui99@gmail.com>
> > > ---
> > > v1: add memory leak fix when not resubmitting urb
> > > v2: add memory leak fix when failing to resubmit urb
> > >
> > >  drivers/net/can/usb/mcba_usb.c | 11 ++++++++---
> > >  1 file changed, 8 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/net/can/usb/mcba_usb.c b/drivers/net/can/usb/mcba_usb.c
> > > index df54eb7d4b36..30236e640116 100644
> > > --- a/drivers/net/can/usb/mcba_usb.c
> > > +++ b/drivers/net/can/usb/mcba_usb.c
> > > @@ -584,6 +584,8 @@ static void mcba_usb_read_bulk_callback(struct urb *urb)
> > >     case -EPIPE:
> > >     case -EPROTO:
> > >     case -ESHUTDOWN:
> > > +           usb_free_coherent(urb->dev, urb->transfer_buffer_length,
> > > +                             urb->transfer_buffer, urb->transfer_dma);
> > >             return;
> > >
> >
> > Can you call usb_free_coherent() in what can be hard IRQ context?
>
> You are right, I digged in the code and saw some comments that on some
> architectures, usb_free_coherent() cannot be called in hard IRQ context.
> I see the usb_free_coherent() is called in write_bulk_callback too. I will
> send a patch that uses usb_anchor to keep track of these urbs and cleanup
> the transfer buffer later in disconnect().

Hi, I have sent a version 3 patch. However, I found out that usb_free_coherent()
is ok in this situation. In usb_free_coherent(), if the buffer is allocated via
dma_alloc_coherent() in usb_alloc_coherent(), dma_free_coherent() is called.
In dma_free_coherent(), ops->free() may be called in some cases which may
contains calls to vunmap() that is not permitted in interrupt context. However,
in usb_alloc_coherent(), buffer can be allocated from dma pool if the
size is less
than 2048 and the buffer size in mcba_usb is obviously less than 2048.
As a result,
usb_free_coherent() will at most fall in the path that calls
dma_pool_free(), which is
safe. Am I right?

Thanks,
Quang Minh.

Re: [PATCH v2] can: mcba_usb: Fix memory leak when cancelling urb

[Bui Quang Minh]

On Tue, Jan 12, 2021 at 01:42:33PM +0700, Minh Bùi Quang wrote:
> On Mon, Jan 11, 2021 at 9:31 PM Bui Quang Minh <minhquangbui99@gmail.com> wrote:
> >
> > On Mon, Jan 11, 2021 at 01:00:31PM +0100, Oliver Neukum wrote:
> > > Am Montag, den 11.01.2021, 10:49 +0000 schrieb Bui Quang Minh:
> > > > In mcba_usb_read_bulk_callback(), when we don't resubmit or fails to
> > > > resubmit the urb, we need to deallocate the transfer buffer that is
> > > > allocated in mcba_usb_start().
> > > >
> > > > Reported-by: syzbot+57281c762a3922e14dfe@syzkaller.appspotmail.com
> > > > Signed-off-by: Bui Quang Minh <minhquangbui99@gmail.com>
> > > > ---
> > > > v1: add memory leak fix when not resubmitting urb
> > > > v2: add memory leak fix when failing to resubmit urb
> > > >
> > > >  drivers/net/can/usb/mcba_usb.c | 11 ++++++++---
> > > >  1 file changed, 8 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/drivers/net/can/usb/mcba_usb.c b/drivers/net/can/usb/mcba_usb.c
> > > > index df54eb7d4b36..30236e640116 100644
> > > > --- a/drivers/net/can/usb/mcba_usb.c
> > > > +++ b/drivers/net/can/usb/mcba_usb.c
> > > > @@ -584,6 +584,8 @@ static void mcba_usb_read_bulk_callback(struct urb *urb)
> > > >     case -EPIPE:
> > > >     case -EPROTO:
> > > >     case -ESHUTDOWN:
> > > > +           usb_free_coherent(urb->dev, urb->transfer_buffer_length,
> > > > +                             urb->transfer_buffer, urb->transfer_dma);
> > > >             return;
> > > >
> > >
> > > Can you call usb_free_coherent() in what can be hard IRQ context?
> >
> > You are right, I digged in the code and saw some comments that on some
> > architectures, usb_free_coherent() cannot be called in hard IRQ context.
> > I see the usb_free_coherent() is called in write_bulk_callback too. I will
> > send a patch that uses usb_anchor to keep track of these urbs and cleanup
> > the transfer buffer later in disconnect().
> 
> Hi, I have sent a version 3 patch. However, I found out that usb_free_coherent()
> is ok in this situation. In usb_free_coherent(), if the buffer is allocated via
> dma_alloc_coherent() in usb_alloc_coherent(), dma_free_coherent() is called.
> In dma_free_coherent(), ops->free() may be called in some cases which may
> contains calls to vunmap() that is not permitted in interrupt context. However,
> in usb_alloc_coherent(), buffer can be allocated from dma pool if the
> size is less
> than 2048 and the buffer size in mcba_usb is obviously less than 2048.
> As a result,
> usb_free_coherent() will at most fall in the path that calls
> dma_pool_free(), which is
> safe. Am I right?

Hi, I'm CC'ing CAN network driver maintainers so we can discuss the patch properly.

I'm so sorry for spamming emails.

Thanks,
Quang Minh.