Re: [PATCH 5.10 26/76] sfc: Check null pointer of rx_queue->page_ring
From: Pavel Machek <hidden>
Date: 2021-12-29 11:17:41
Also in:
lkml
hi!
From: Jiasheng Jiang <redacted> [ 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.
quoted hunk ↗ jump to hunk
+++ 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.
Best regards,
Pavel
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