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author | David Hildenbrand <david@redhat.com> | 2019-07-22 15:41:04 +0200 |
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committer | Michael S. Tsirkin <mst@redhat.com> | 2019-07-25 07:57:52 -0400 |
commit | 483f13524bb2a08b7ff6a7560b846564ed3b0c33 (patch) | |
tree | fa08024c4f66a5ab38f7cffb0a7e649248e77cd5 /hw/virtio | |
parent | ffa207d08253ffffb3993a1dbe09e40af4fc91f1 (diff) | |
download | qemu-483f13524bb2a08b7ff6a7560b846564ed3b0c33.zip qemu-483f13524bb2a08b7ff6a7560b846564ed3b0c33.tar.gz qemu-483f13524bb2a08b7ff6a7560b846564ed3b0c33.tar.bz2 |
virtio-balloon: Fix QEMU crashes on pagesize > BALLOON_PAGE_SIZE
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
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20190722134108.22151-3-david@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'hw/virtio')
-rw-r--r-- | hw/virtio/virtio-balloon.c | 10 |
1 files changed, 4 insertions, 6 deletions
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c index 515abf6..a78d2d2 100644 --- a/hw/virtio/virtio-balloon.c +++ b/hw/virtio/virtio-balloon.c @@ -94,9 +94,8 @@ static void balloon_inflate_page(VirtIOBalloon *balloon, balloon->pbp->base = host_page_base; } - bitmap_set(balloon->pbp->bitmap, - (ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE, - subpages); + set_bit((ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE, + balloon->pbp->bitmap); if (bitmap_full(balloon->pbp->bitmap, subpages)) { /* We've accumulated a full host page, we can actually discard @@ -140,9 +139,8 @@ static void balloon_deflate_page(VirtIOBalloon *balloon, * for a guest to do this in practice, but handle it anyway, * since getting it wrong could mean discarding memory the * guest is still using. */ - bitmap_clear(balloon->pbp->bitmap, - (ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE, - subpages); + clear_bit((ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE, + balloon->pbp->bitmap); if (bitmap_empty(balloon->pbp->bitmap, subpages)) { g_free(balloon->pbp); |