Re: [PATCH] Fix guest memory leak and panic

From: David Miller
Date: Tue Oct 18 2011 - 15:14:49 EST


From: Krishna Kumar <krkumar2@xxxxxxxxxx>
Date: Tue, 18 Oct 2011 13:35:23 +0530

> Commit 86ee8130 ("virtionet: convert to SKB paged frag API")
> introduced a bug in guest. During RX testing, guest runs out
> of memory within seconds, causing oom-killer; which then
> panics the system: "Kernel panic - not syncing: Out of memory
> and no killable processes...". /proc/meminfo just before the
> panic shows MemFree is a few MB's:
>
> MemFree: 1928544 kB (starts here)
> ...
> ...
> MemFree: 27488 kB
> MemFree: 26248 kB
> MemFree: 24636 kB
> MemFree: 22632 kB
> MemFree: 19580 kB
> MemFree: 17928 kB
> MemFree: 15548 kB
> (Panic)
>
> The extra reference to the fragment pages causes those pages to
> not get freed in skb_release_data(). The following patch fixes
> the bug. I have not checked if any other converted driver has
> the same issue.
>
> Signed-off-by: Krishna Kumar <krkumar2@xxxxxxxxxx>

I'll wait for Ian's full audit, but Krishna please use more appropriate
subject lines in future patch submissions.

This patch is fixing a problem in the virtio_net driver, so please
mention that: "Subject: [PATCH] virtio_net: Fix guest memory leak and panic"
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