It appears that under certain circumstances, a race will result
in a double-free of an skb. This patch null's out the skb pointer
upon the skb free, avoiding the inadvertent deref of bogus data.
The next patch fixes the actual race.
Signed-off-by: Linas Vepstas <[EMAIL PROTECTED]>
Cc: James K Lewis <[EMAIL PROTECTED]>
Cc: Jens Osterkamp <[EMAIL PROTECTED]>
Cc: Kou Ishizaki <[EMAIL PROTECTED]>
----
drivers/net/spider_net.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
Index: linux-2.6.20-git4/drivers/net/spider_net.c
===================================================================
--- linux-2.6.20-git4.orig/drivers/net/spider_net.c 2007-02-09
16:56:25.000000000 -0600
+++ linux-2.6.20-git4/drivers/net/spider_net.c 2007-02-09 16:56:30.000000000
-0600
@@ -360,10 +360,11 @@ spider_net_free_rx_chain_contents(struct
descr = card->rx_chain.head;
do {
if (descr->skb) {
- dev_kfree_skb(descr->skb);
pci_unmap_single(card->pdev, descr->hwdescr->buf_addr,
SPIDER_NET_MAX_FRAME,
PCI_DMA_BIDIRECTIONAL);
+ dev_kfree_skb(descr->skb);
+ descr->skb = NULL;
}
descr = descr->next;
} while (descr != card->rx_chain.head);
@@ -417,6 +418,7 @@ spider_net_prepare_rx_descr(struct spide
SPIDER_NET_MAX_FRAME, PCI_DMA_FROMDEVICE);
if (pci_dma_mapping_error(buf)) {
dev_kfree_skb_any(descr->skb);
+ descr->skb = NULL;
if (netif_msg_rx_err(card) && net_ratelimit())
pr_err("Could not iommu-map rx buffer\n");
card->spider_stats.rx_iommu_map_error++;
@@ -646,6 +648,7 @@ static int
spider_net_prepare_tx_descr(struct spider_net_card *card,
struct sk_buff *skb)
{
+ struct spider_net_descr_chain *chain = &card->tx_chain;
struct spider_net_descr *descr;
struct spider_net_hw_descr *hwdescr;
dma_addr_t buf;
@@ -660,10 +663,15 @@ spider_net_prepare_tx_descr(struct spide
return -ENOMEM;
}
- spin_lock_irqsave(&card->tx_chain.lock, flags);
+ spin_lock_irqsave(&chain->lock, flags);
descr = card->tx_chain.head;
+ if (descr->next == chain->tail->prev) {
+ spin_unlock_irqrestore(&chain->lock, flags);
+ pci_unmap_single(card->pdev, buf, skb->len, PCI_DMA_TODEVICE);
+ return -ENOMEM;
+ }
hwdescr = descr->hwdescr;
- card->tx_chain.head = descr->next;
+ chain->head = descr->next;
descr->skb = skb;
hwdescr->buf_addr = buf;
@@ -673,7 +681,7 @@ spider_net_prepare_tx_descr(struct spide
hwdescr->dmac_cmd_status =
SPIDER_NET_DESCR_CARDOWNED | SPIDER_NET_DMAC_NOCS;
- spin_unlock_irqrestore(&card->tx_chain.lock, flags);
+ spin_unlock_irqrestore(&chain->lock, flags);
if (skb->protocol == htons(ETH_P_IP))
switch (skb->nh.iph->protocol) {
@@ -802,6 +810,7 @@ spider_net_release_tx_chain(struct spide
chain->tail = descr->next;
hwdescr->dmac_cmd_status |= SPIDER_NET_DESCR_NOT_IN_USE;
skb = descr->skb;
+ descr->skb = NULL;
buf_addr = hwdescr->buf_addr;
spin_unlock_irqrestore(&chain->lock, flags);
@@ -867,13 +876,10 @@ spider_net_xmit(struct sk_buff *skb, str
{
int cnt;
struct spider_net_card *card = netdev_priv(netdev);
- struct spider_net_descr_chain *chain = &card->tx_chain;
spider_net_release_tx_chain(card, 0);
- if ((chain->head->next == chain->tail->prev) ||
- (spider_net_prepare_tx_descr(card, skb) != 0)) {
-
+ if (spider_net_prepare_tx_descr(card, skb) != 0) {
card->netdev_stats.tx_dropped++;
netif_stop_queue(netdev);
return NETDEV_TX_BUSY;
@@ -1091,6 +1097,7 @@ spider_net_decode_one_descr(struct spide
bad_desc:
dev_kfree_skb_irq(descr->skb);
+ descr->skb = NULL;
hwdescr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
return 0;
}
-
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