On Wed, Dec 29, 2021 at 12:17:30PM +0100, Pavel Machek wrote: > hi! > > > From: Jiasheng Jiang <jiasheng@xxxxxxxxxxx> > > > > [ Upstream commit bdf1b5c3884f6a0dc91b0dbdb8c3b7d205f449e0 ] > > > > Because of the possible failure of the kcalloc, it should be better to > > set rx_queue->page_ptr_mask to 0 when it happens in order to maintain > > the consistency. > > This is confusing/wrong, or at least not a complete fix. > > > +++ b/drivers/net/ethernet/sfc/rx_common.c > > @@ -150,7 +150,10 @@ static void efx_init_rx_recycle_ring(struct efx_rx_queue *rx_queue) > > efx->rx_bufs_per_page); > > rx_queue->page_ring = kcalloc(page_ring_size, > > sizeof(*rx_queue->page_ring), GFP_KERNEL); > > - rx_queue->page_ptr_mask = page_ring_size - 1; > > + if (!rx_queue->page_ring) > > + rx_queue->page_ptr_mask = 0; > > + else > > + rx_queue->page_ptr_mask = page_ring_size - 1; > > } > > > > So we have !rx_queue->page_ring. But in efx_reuse_page, we do > > index = rx_queue->page_remove & rx_queue->page_ptr_mask; > page = rx_queue->page_ring[index]; > > So index is now zero, but we'll derefernce null pointer anyway. Good point. I've posted a patch for this to netdev. https://lore.kernel.org/netdev/164103678041.26263.8354809911405746465.stgit@xxxxxxxxxxxxxxxxxx/ Thanks, Martin
