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spidernet: fix racy double-free of skb

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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 <linas@austin.ibm.com>
Cc: Jens Osterkamp <Jens.Osterkamp@de.ibm.com>
Cc: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
This commit is contained in:
Linas Vepstas 2007-02-20 16:41:03 -06:00 committed by Jeff Garzik
parent 4cb6f9e57d
commit d9c199ee78
1 changed files with 15 additions and 8 deletions
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23
drivers/net/spider_net.c
View file

@ -396,10 +396,11 @@ spider_net_free_rx_chain_contents(struct spider_net_card *card)
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);
@ -453,6 +454,7 @@ spider_net_prepare_rx_descr(struct spider_net_card *card,
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++;
@ -682,6 +684,7 @@ 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;
@ -696,10 +699,15 @@ spider_net_prepare_tx_descr(struct spider_net_card *card,
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;
@ -709,7 +717,7 @@ spider_net_prepare_tx_descr(struct spider_net_card *card,
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) {
@ -838,6 +846,7 @@ spider_net_release_tx_chain(struct spider_net_card *card, int brutal)
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);
@ -903,13 +912,10 @@ spider_net_xmit(struct sk_buff *skb, struct net_device *netdev)
{
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;
@ -1127,6 +1133,7 @@ spider_net_decode_one_descr(struct spider_net_card *card)
bad_desc:
dev_kfree_skb_irq(descr->skb);
descr->skb = NULL;
hwdescr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
return 0;
}