Re: [PATCH] rtlwifi: get buffer_desc before trying to alloc new skb

From: Larry Finger
Date: Thu Mar 12 2015 - 12:03:10 EST

On 03/12/2015 06:33 AM, Yang Bai wrote:
if rtlpriv->use_new_trx_flow == true and we run out of memory
to alloc a new skb, we will directly jump to no_new tag with
buffer_desc == NULL. Then we will dereference this NULL pointer
in function _rtl_pci_init_one_rxdesc.

Signed-off-by: Yang Bai <>

Good catch. The only problem that I have is this fix adds even more branching to this interrupt routine. At first glance, I should be able to set buffer_desc in the earlier code where the code has already branched. For testing, an RTL8192EE card will be needed. Do you have such a card?


drivers/net/wireless/rtlwifi/pci.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/rtlwifi/pci.c b/drivers/net/wireless/rtlwifi/pci.c
index a62170e..7fe04d1 100644
--- a/drivers/net/wireless/rtlwifi/pci.c
+++ b/drivers/net/wireless/rtlwifi/pci.c
@@ -820,17 +820,19 @@ static void _rtl_pci_rx_interrupt(struct ieee80211_hw *hw)
pci_unmap_single(rtlpci->pdev, *((dma_addr_t *)skb->cb),
rtlpci->rxbuffersize, PCI_DMA_FROMDEVICE);

+ if (rtlpriv->use_new_trx_flow)
+ buffer_desc =
+ &rtlpci->rx_ring[rxring_idx].buffer_desc
+ [rtlpci->rx_ring[rxring_idx].idx];
/* get a new skb - if fail, old one will be reused */
new_skb = dev_alloc_skb(rtlpci->rxbuffersize);
if (unlikely(!new_skb))
goto no_new;
- if (rtlpriv->use_new_trx_flow) {
- buffer_desc =
- &rtlpci->rx_ring[rxring_idx].buffer_desc
- [rtlpci->rx_ring[rxring_idx].idx];
+ if (rtlpriv->use_new_trx_flow)
/*means rx wifi info*/
pdesc = (struct rtl_rx_desc *)skb->data;
- }
memset(&rx_status , 0 , sizeof(rx_status));
rtlpriv->cfg->ops->query_rx_desc(hw, &stats,
&rx_status, (u8 *)pdesc, skb);

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