From: David Hildenbrand <david@redhat.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: Igor Mammedov <imammedo@redhat.com>,
qemu-stable@nongnu.org, qemu-devel@nongnu.org,
Stefan Hajnoczi <stefanha@redhat.com>,
"Michael S . Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] [PATCH-for-4.1 v2 1/3] virtio-balloon: fix QEMU crashes on pagesize > BALLOON_PAGE_SIZE
Date: Thu, 18 Jul 2019 13:50:33 +0200 [thread overview]
Message-ID: <84e011f3-06cc-d510-ba75-97ca4e9568d2@redhat.com> (raw)
In-Reply-To: <20190718035032.GC8468@umbus.fritz.box>
On 18.07.19 05:50, David Gibson wrote:
> On Wed, Jul 17, 2019 at 12:35:48PM +0200, David Hildenbrand wrote:
>> We are using the wrong functions to set/clear bits, effectively touching
>> multiple bits, writing out of range of the bitmap, resulting in memory
>> corruptions. We have to use set_bit()/clear_bit() instead.
>>
>> Can easily be reproduced by starting a qemu guest on hugetlbfs memory,
>> inflating the balloon. QEMU crashes. This never could have worked
>> properly - especially, also pages would have been discarded when the
>> first sub-page would be inflated (the whole bitmap would be set).
>>
>> While testing I realized, that on hugetlbfs it is pretty much impossible
>> to discard a page - the guest just frees the 4k sub-pages in random order
>> most of the time. I was only able to discard a hugepage a handful of
>> times - so I hope that now works correctly.
>>
>> Fixes: ed48c59875b6 ("virtio-balloon: Safely handle BALLOON_PAGE_SIZE <
>> host page size")
>> Fixes: b27b32391404 ("virtio-balloon: Fix possible guest memory corruption
>> with inflates & deflates")
>> Cc: qemu-stable@nongnu.org #v4.0.0
>> Cc: Stefan Hajnoczi <stefanha@redhat.com>
>> Cc: David Gibson <david@gibson.dropbear.id.au>
>> Cc: Michael S. Tsirkin <mst@redhat.com>
>> Cc: Igor Mammedov <imammedo@redhat.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>
> Ahem. You can pass me the brown paper bag now.
>
No worries, BUGs are inevitable.
Thanks!
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2019-07-18 11:50 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-17 10:35 [Qemu-devel] [PATCH-for-4.1 v2 0/3] virtio-balloon: fixes for PartialBalloonedPage David Hildenbrand
2019-07-17 10:35 ` [Qemu-devel] [PATCH-for-4.1 v2 1/3] virtio-balloon: fix QEMU crashes on pagesize > BALLOON_PAGE_SIZE David Hildenbrand
2019-07-18 3:50 ` David Gibson
2019-07-18 11:50 ` David Hildenbrand [this message]
2019-07-17 10:35 ` [Qemu-devel] [PATCH-for-4.1 v2 2/3] virtio-balloon: fix memory leak on unrealize() David Hildenbrand
2019-07-18 3:51 ` David Gibson
2019-07-17 10:35 ` [Qemu-devel] [PATCH-for-4.1 v2 3/3] virtio-balloon: reset pbp on device resets David Hildenbrand
2019-07-17 10:48 ` Michael S. Tsirkin
2019-07-17 11:06 ` David Hildenbrand
2019-07-17 11:29 ` Michael S. Tsirkin
2019-07-17 11:32 ` David Hildenbrand
2019-07-18 3:52 ` David Gibson
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