Bcc: Subject: Re: [PATCH v2] can: mcba_usb: Fix memory leak when cancelling urb Reply-To: In-Reply-To: <CACtPs=FB_=jmeymlhe0_ko4zf5zj9nbchkrc7o3tj6pksp3...@mail.gmail.com>
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 <minhquangbu...@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+57281c762a3922e14...@syzkaller.appspotmail.com > > > > Signed-off-by: Bui Quang Minh <minhquangbu...@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. Thanks, Quang Minh.
