Re: [Bugme-new] [Bug 38102] New: BUG kmalloc-2048: Poison overwritten

[Eric Dumazet <eric.dumazet@gmail.com>]

Le dimanche 03 juillet 2011 à 01:25 +0400, Alexey Zaytsev a écrit :
> On Fri, Jul 1, 2011 at 10:01, Alexey Zaytsev <alexey.zaytsev@gmail.com> wrote:
> > On Thu, Jun 30, 2011 at 01:51, Andrew Morton <akpm@linux-foundation.org> wrote:
> >>
> >> (switched to email.  Please respond via emailed reply-to-all, not via the
> >> bugzilla web interface).
> >>
> >> On Thu, 23 Jun 2011 17:33:54 GMT
> >> bugzilla-daemon@bugzilla.kernel.org wrote:
> >>
> >>> https://bugzilla.kernel.org/show_bug.cgi?id=38102
> >>>
> >>>            Summary: BUG kmalloc-2048: Poison overwritten
> >>>            Product: Drivers
> >>>            Version: 2.5
> >>>     Kernel Version: 3.0.0-rc4
> >>
> >> Looks like a 2.6.38->2.6.39 regression, perhaps a memory scribble in b44.
> >
> > Actually, not sure about the version. 39 was the first one I've been
> > using in the scenario. Checking older versions now.
> > And git-log does not show a lot of changes to the b44 driver, so it
> > might be something unrelated.
> >
> 
> I've checked back as far as 2.6.27, and the problem is still there.
> I've also looked through the allocation-related code, and it seemed
> sane. I'm not sure I understand the 1GB dma workaround, but this path
> is never hit in my case. So adding the driver authors to CC. This
> could be something different, but I've been unable to reproduce using
> an other machine with an rtl8139 nic.

Hmm, looking at b44 code, I believe there is a race there.

Could you try following patch ?

Thanks

diff --git a/drivers/net/b44.c b/drivers/net/b44.c
index a69331e..80f2fdc 100644
--- a/drivers/net/b44.c
+++ b/drivers/net/b44.c
@@ -689,9 +689,9 @@ static int b44_alloc_rx_skb(struct b44 *bp, int src_idx, u32 dest_idx_unmasked)
 		ctrl |= DESC_CTRL_EOT;
 
 	dp = &bp->rx_ring[dest_idx];
-	dp->ctrl = cpu_to_le32(ctrl);
 	dp->addr = cpu_to_le32((u32) mapping + bp->dma_offset);
-
+	wmb();
+	dp->ctrl = cpu_to_le32(ctrl);
 	if (bp->flags & B44_FLAG_RX_RING_HACK)
 		b44_sync_dma_desc_for_device(bp->sdev, bp->rx_ring_dma,
 			                    dest_idx * sizeof(*dp),