On Mon, Jan 11, 2021 at 9:31 PM Bui Quang Minh <minhquangbui99@xxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxxxxxx > > > Signed-off-by: Bui Quang Minh <minhquangbui99@xxxxxxxxx> > > > --- > > > 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.
