From: linas@austin.ibm.com (Linas Vepstas)
To: Jeff Garzik <jeff@garzik.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
kou.ishizaki@toshiba.co.jp, arnd@arndb.de,
Jens Osterkamp <jens@de.ibm.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 9/12]: spidernet: fix racy double-free of skb
Date: Tue, 20 Feb 2007 16:41:03 -0600 [thread overview]
Message-ID: <20070220224103.GI28895@austin.ibm.com> (raw)
In-Reply-To: <20070220221314.GU923@austin.ibm.com>
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>
----
drivers/net/spider_net.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
Index: linux-2.6.20-git16/drivers/net/spider_net.c
===================================================================
--- linux-2.6.20-git16.orig/drivers/net/spider_net.c 2007-02-20 15:02:44.000000000 -0600
+++ linux-2.6.20-git16/drivers/net/spider_net.c 2007-02-20 15:02:46.000000000 -0600
@@ -396,10 +396,11 @@ 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);
@@ -453,6 +454,7 @@ 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++;
@@ -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 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;
@@ -709,7 +717,7 @@ 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) {
@@ -838,6 +846,7 @@ 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);
@@ -903,13 +912,10 @@ 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;
@@ -1127,6 +1133,7 @@ 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;
}
next prev parent reply other threads:[~2007-02-20 22:41 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-20 22:13 [PATCH 0/12]: spidernet updates Linas Vepstas
2007-02-20 22:30 ` [PATCH 1/12]: sungem_phy: support bcm5461 phy, autoneg Linas Vepstas
2007-02-27 9:16 ` Jeff Garzik
2007-02-20 22:32 ` [PATCH 2/12] spidernet: compile break Linas Vepstas
2007-02-20 22:33 ` [PATCH 3/12] spidernet: autoneg support for Celleb Linas Vepstas
2007-02-20 22:34 ` [PATCH 4/12] spidernet: load firmware when open Linas Vepstas
2007-02-20 22:36 ` [PATCH 5/12] spidernet: spidernet: add support for Celleb Linas Vepstas
2007-02-20 22:37 ` [PATCH 6/12] spidernet: remove txram full logging Linas Vepstas
2007-02-20 22:39 ` [PATCH 7/12] spidernet: move medium variable into card struct Linas Vepstas
2007-02-20 22:40 ` [PATCH 8/12] spidernet: separate hardware state from driver state Linas Vepstas
2007-02-20 22:41 ` Linas Vepstas [this message]
2007-02-20 22:41 ` [PATCH 10/12]: spidernet: transmit race Linas Vepstas
2007-02-20 22:42 ` [PATCH 11/12] spidernet: janitorial, typos Linas Vepstas
2007-02-20 22:45 ` [PATCH 12/12] spidernet: maintainership Linas Vepstas
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