[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v2 for-1.5 1/4] qcow2: Catch some L1 table index
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH v2 for-1.5 1/4] qcow2: Catch some L1 table index overflows |
Date: |
Tue, 14 May 2013 16:49:24 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, May 14, 2013 at 04:14:33PM +0200, Kevin Wolf wrote:
> This catches the situation that is described in the bug report at
> https://bugs.launchpad.net/qemu/+bug/865518 and goes like this:
>
> $ qemu-img create -f qcow2 huge.qcow2 $((1024*1024))T
> Formatting 'huge.qcow2', fmt=qcow2 size=1152921504606846976
> encryption=off cluster_size=65536 lazy_refcounts=off
> $ qemu-io /tmp/huge.qcow2 -c "write $((1024*1024*1024*1024*1024*1024 -
> 1024)) 512"
> Segmentation fault
>
> With this patch applied the segfault will be avoided, however the case
> will still fail, though gracefully:
>
> $ qemu-img create -f qcow2 /tmp/huge.qcow2 $((1024*1024))T
> Formatting 'huge.qcow2', fmt=qcow2 size=1152921504606846976
> encryption=off cluster_size=65536 lazy_refcounts=off
> qemu-img: The image size is too large for file format 'qcow2'
>
> Note that even long before these overflow checks kick in, you get
> insanely high memory usage (up to INT_MAX * sizeof(uint64_t) = 16 GB for
> the L1 table), so with somewhat smaller image sizes you'll probably see
> qemu aborting for a failed g_malloc().
>
> If you need huge image sizes, you should increase the cluster size to
> the maximum of 2 MB in order to get higher limits.
>
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
> block/qcow2-cluster.c | 23 +++++++++++++++--------
> block/qcow2.c | 13 +++++++++++--
> block/qcow2.h | 5 +++--
> 3 files changed, 29 insertions(+), 12 deletions(-)
Thanks, applied to my block tree for 1.5:
https://github.com/stefanha/qemu/commits/block
Stefan
- [Qemu-devel] [PATCH v2 for-1.5 0/4] qcow2: Catch some L1 table index overflows, Kevin Wolf, 2013/05/14
- [Qemu-devel] [PATCH v2 3/4] qcow2.py: Subcommand for changing header fields, Kevin Wolf, 2013/05/14
- [Qemu-devel] [PATCH v2 for-1.5 1/4] qcow2: Catch some L1 table index overflows, Kevin Wolf, 2013/05/14
- Re: [Qemu-devel] [PATCH v2 for-1.5 1/4] qcow2: Catch some L1 table index overflows,
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH v2 for-1.5 2/4] block: Add hint to -EFBIG error message, Kevin Wolf, 2013/05/14
- [Qemu-devel] [PATCH v2 4/4] qemu-iotests: Try creating huge qcow2 image, Kevin Wolf, 2013/05/14
- Re: [Qemu-devel] [PATCH v2 for-1.5 0/4] qcow2: Catch some L1 table index overflows, Richard W.M. Jones, 2013/05/14
- Re: [Qemu-devel] [PATCH v2 for-1.5 0/4] qcow2: Catch some L1 table index overflows, Stefan Hajnoczi, 2013/05/15