Re: [PATCH] net: mscc: fix in frame extraction

[David Miller <davem@davemloft.net>]

From: Horatiu Vultur <horatiu.vultur@microchip.com>
Date: Mon, 17 Feb 2020 09:31:33 +0100

> Each extracted frame on Ocelot has an IFH. The frame and IFH are extracted
> by reading chuncks of 4 bytes from a register.
> 
> In case the IFH and frames were read corretly it would try to read the next
> frame. In case there are no more frames in the queue, it checks if there
> were any previous errors and in that case clear the queue. But this check
> will always succeed also when there are no errors. Because when extracting
> the IFH the error is checked against 4(number of bytes read) and then the
> error is set only if the extraction of the frame failed. So in a happy case
> where there are no errors the err variable is still 4. So it could be
> a case where after the check that there are no more frames in the queue, a
> frame will arrive in the queue but because the error is not reseted, it
> would try to flush the queue. So the frame will be lost.
> 
> The fix consist in resetting the error after reading the IFH.
> 
> Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>

Applied and queued up for -stable.