Quoted 31 lines · Bui Quang Minh

Quoted 14 lines · Oliver Neukum

Am Montag, den 11.01.2021, 10:49 +0000 schrieb Bui Quang Minh:

Quoted 13 lines

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 [email protected]

Signed-off-by Bui Quang Minh <[email protected]>

---
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(-)

Quoted 14 lines

drivers/net/can/usb/mcba_usb.c static void mcba_usb_read_bulk_callback(struct urb *urb) · line 590

Quoted 12 lines

drivers/net/can/usb/mcba_usb.c +2 -0

index df54eb7d4b36..30236e640116 100644
@@ -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?

Quoted 5 lines

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?