Re: e100 REGRESSION in 2.6.32 (PATCH)

From: Alan Stern
Date: Thu Dec 17 2009 - 10:47:43 EST


On Thu, 17 Dec 2009, Roger Oksanen wrote:

> e100: Fix broken cbs accounting due to missing memset.
>
> Alan Stern noticed that e100 caused slab corruption.
> commit 98468efddb101f8a29af974101c17ba513b07be1 changed
> the allocation of cbs to use dma pools that don't return zeroed memory,
> especially the cb->status field used to track which cb to clean, causing
> (the visible) double freeing of skbs and a wrong free cbs count.
>
> Now the cbs are explicitly zeroed at allocation time.
>
> Reported-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Roger Oksanen <roger.oksanen@xxxxxxxxxxxxxx>
> ---
> drivers/net/e100.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/net/e100.c b/drivers/net/e100.c
> index d269a68..29a8840 100644
> --- a/drivers/net/e100.c
> +++ b/drivers/net/e100.c
> @@ -1815,6 +1815,7 @@ static int e100_alloc_cbs(struct nic *nic)
>
> nic->cbs = pci_pool_alloc(nic->cbs_pool, GFP_KERNEL,
> &nic->cbs_dma_addr);
> + memset(nic->cbs, 0, count * sizeof(struct cb));
> if (!nic->cbs)
> return -ENOMEM;
>
> @@ -1825,7 +1826,6 @@ static int e100_alloc_cbs(struct nic *nic)
> cb->dma_addr = nic->cbs_dma_addr + i * sizeof(struct cb);
> cb->link = cpu_to_le32(nic->cbs_dma_addr +
> ((i+1) % count) * sizeof(struct cb));
> - cb->skb = NULL;
> }
>
> nic->cb_to_use = nic->cb_to_send = nic->cb_to_clean = nic->cbs;

Clearly the memset() belongs after the "if" test, not before. Apart
from that, I confirm that this patch fixes the problem in 2.6.32.

Tested-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>

Alan Stern

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