On 30.10.2021 01:35:01, Vincent MAILHOL wrote: > On Fri. 29 Oct 2021 at 20:34, Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> wrote: > > On 27.10.2021 03:09:09, Vincent Mailhol wrote: > > > In m_can_read_fifo(), if the second call to m_can_fifo_read() fails, > > > the function jump to the out_fail label and returns without calling > > > m_can_receive_skb(). This means that the skb previously allocated by > > > alloc_can_skb() is not freed. In other terms, this is a memory leak. > > > > > > This patch adds a new goto statement: out_receive_skb and do some > > > small code refactoring to fix the issue. > > > > This means we pass a skb to the user space, which contains wrong data. > > Probably 0x0, but if the CAN frame doesn't contain 0x0, it's wrong. That > > doesn't look like a good idea. If the CAN frame broke due to a CRC issue > > on the wire it is not received. IMHO it's best to discard the skb and > > return the error. > > Arg... Guess I made the right choice to tag the patch as RFC... > > Just one question, what is the correct function to discard the > skb? The driver uses the napi polling system (which I am not > entirely familiar with). Does it mean that the rx is not done in > IRQ context and that we can simply use kfree_skb() instead of > dev_kfree_skb_irq()? The m_can driver is a bit more complicated. It uses NAPI for mmio devices, but threaded IRQs for SPI devices. Looking at dev_kfree_skb_any(), it checks for hard IRQs or IRQs disabled, I think this is not the case for both threaded IRQs and NAPI. https://elixir.bootlin.com/linux/v5.15/source/net/core/dev.c#L3108 So I think kfree_skb() should be OK. regards, Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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