2007-01-23 16:59:08

by Dale Farnsworth

Subject: [PATCH] mv643xx_eth: Fix race condition in mv643xx_eth_free_tx_descs

>From Dale Farnsworth <[email protected]>

mv643xx_eth: Fix race condition in mv643xx_eth_free_tx_descs

This bug was found and isolated by Thibaut VARENE <[email protected]>
and Jarek Poplawski <[email protected]>. This patch is a modification of their
fixes. We acquire and release the lock for each descriptor that is freed
to minimize the time the lock is held.

---

drivers/net/mv643xx_eth.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mv643xx_eth.c b/drivers/net/mv643xx_eth.c
index c41ae42..b3bf864 100644
--- a/drivers/net/mv643xx_eth.c
+++ b/drivers/net/mv643xx_eth.c
@@ -314,6 +314,13 @@ int mv643xx_eth_free_tx_descs(struct net

while (mp->tx_desc_count > 0) {
spin_lock_irqsave(&mp->lock, flags);
+
+ /* tx_desc_count might have changed before acquiring the lock */
+ if (mp->tx_desc_count <= 0) {
+ spin_unlock_irqrestore(&mp->lock, flags);
+ return released;
+ }
+
tx_index = mp->tx_used_desc_q;
desc = &mp->p_tx_desc_area[tx_index];
cmd_sts = desc->cmd_sts;
@@ -332,13 +339,13 @@ int mv643xx_eth_free_tx_descs(struct net
if (skb)
mp->tx_skb[tx_index] = NULL;

- spin_unlock_irqrestore(&mp->lock, flags);
-
if (cmd_sts & ETH_ERROR_SUMMARY) {
printk("%s: Error in TX\n", dev->name);
mp->stats.tx_errors++;
}

+ spin_unlock_irqrestore(&mp->lock, flags);
+
if (cmd_sts & ETH_TX_FIRST_DESC)
dma_unmap_single(NULL, addr, count, DMA_TO_DEVICE);
else

2007-01-23 17:03:05

by Thibaut VARENE

Subject: Re: [PATCH] mv643xx_eth: Fix race condition in mv643xx_eth_free_tx_descs

On 1/23/07, Dale Farnsworth <[email protected]> wrote:
> From Dale Farnsworth <[email protected]>
>
> mv643xx_eth: Fix race condition in mv643xx_eth_free_tx_descs
>
> This bug was found and isolated by Thibaut VARENE <[email protected]>
> and Jarek Poplawski <[email protected]>. This patch is a modification of their
> fixes. We acquire and release the lock for each descriptor that is freed
> to minimize the time the lock is held.
>
> ---
>
> drivers/net/mv643xx_eth.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/mv643xx_eth.c b/drivers/net/mv643xx_eth.c
> index c41ae42..b3bf864 100644
> --- a/drivers/net/mv643xx_eth.c
> +++ b/drivers/net/mv643xx_eth.c
> @@ -332,13 +339,13 @@ int mv643xx_eth_free_tx_descs(struct net
> if (skb)
> mp->tx_skb[tx_index] = NULL;
>
> - spin_unlock_irqrestore(&mp->lock, flags);
> -
> if (cmd_sts & ETH_ERROR_SUMMARY) {
> printk("%s: Error in TX\n", dev->name);
> mp->stats.tx_errors++;
> }

Note that this printk probably won't show immediately because IRQs are
disabled. But that's maybe not a big deal.

HTH

--
Thibaut VARENE
http://www.parisc-linux.org/~varenet/

2007-01-23 21:29:50

by Jeff Garzik

Subject: Re: [PATCH] mv643xx_eth: Fix race condition in mv643xx_eth_free_tx_descs

Dale Farnsworth wrote:
>>From Dale Farnsworth <[email protected]>
>
> mv643xx_eth: Fix race condition in mv643xx_eth_free_tx_descs
>
> This bug was found and isolated by Thibaut VARENE <[email protected]>
> and Jarek Poplawski <[email protected]>. This patch is a modification of their
> fixes. We acquire and release the lock for each descriptor that is freed
> to minimize the time the lock is held.
>
> ---
>
> drivers/net/mv643xx_eth.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)

applied