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:

quoted

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 <redacted>
---
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.