Patchwork [1/2] qcow2: Fix refcount table size calculation

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Submitter Kevin Wolf
Date Oct. 26, 2012, 7:42 p.m.
Message ID <1351280528-21889-2-git-send-email-kwolf@redhat.com>
Download mbox | patch
Permalink /patch/194559/
State New
Headers show

Comments

Kevin Wolf - Oct. 26, 2012, 7:42 p.m.
A missing factor for the refcount table entry size in the calculation
could mean that too little memory was allocated for the in-memory
representation of the table, resulting in a buffer overflow.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow2-refcount.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
Michael Tokarev - Oct. 27, 2012, 9:57 a.m.
On 26.10.2012 23:42, Kevin Wolf wrote:
> A missing factor for the refcount table entry size in the calculation
> could mean that too little memory was allocated for the in-memory
> representation of the table, resulting in a buffer overflow.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Reviewed-and-tested-by: Michael Tokarev <mjt@tls.msk.ru>

(but the thing is rather trivial and obvious :)
(this fixes https://bugs.launchpad.net/qemu/+bug/1071236 fwiw --
maybe we should add some references to bugs when the work/patch
is after a bugreport)

This fix is applicable to -stable, at least to 1.2 and 1.1 versions.
For 0.15, while the patch applies, qcow2 driver has other bug(s)
which prevents the testcase (with qemu-img create) from working:

 $ ./qemu-img-0.15 create -f qcow2 -o cluster_size=512,preallocation=metadata disk.img 4G
 Formatting 'disk.img', fmt=qcow2 size=4294967296 encryption=off cluster_size=512 preallocation='metadata'
 qemu-img: disk.img: error while creating qcow2: Unknown error 1652533248

Thanks,

/mjt

Patch

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 5e3f915..96224d1 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -301,7 +301,8 @@  static int alloc_refcount_block(BlockDriverState *bs,
     uint64_t last_table_size;
     uint64_t blocks_clusters;
     do {
-        uint64_t table_clusters = size_to_clusters(s, table_size);
+        uint64_t table_clusters =
+            size_to_clusters(s, table_size * sizeof(uint64_t));
         blocks_clusters = 1 +
             ((table_clusters + refcount_block_clusters - 1)
             / refcount_block_clusters);