build_skb() returns NULL in case of a memory allocation failure so handle
it inside __octep_oq_process_rx() to avoid NULL pointer dereference.
__octep_oq_process_rx() is called during NAPI polling by the driver. If
skb allocation fails, keep on pulling packets out of the Rx DMA queue: we
shouldn't break the polling immediately and thus falsely indicate to the
octep_napi_poll() that the Rx pressure is going down. As there is no
associated skb in this case, don't process the packets and don't push them
up the network stack - they are skipped.
The common code with skb and some index manipulations is extracted to make
the fix more readable and avoid code duplication. Also helper function is
implemented to unmmap/flush all the fragment buffers used by the dropped
packet. 'alloc_failures' counter is incremented to mark the skb allocation
error in driver statistics.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Fixes: 37d79d059606 ("octeon_ep: add Tx/Rx processing and interrupt support")
Suggested-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Suggested-by: Simon Horman <horms@xxxxxxxxxx>
Signed-off-by: Aleksandr Mishin <amishin@xxxxxxxxxx>
---
A similar situation is present in the __octep_vf_oq_process_rx() of the
Octeon VF driver. First we want to try the fix on __octep_oq_process_rx().
Compile tested only.