Patchwork [5/5] qcow2: Fix corruption after error in update_refcount

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Submitter Kevin Wolf
Date May 28, 2010, 11:22 a.m.
Message ID <1275045773-26963-6-git-send-email-kwolf@redhat.com>
Download mbox | patch
Permalink /patch/53887/
State New
Headers show

Comments

Kevin Wolf - May 28, 2010, 11:22 a.m.
After it is done with updating refcounts in the cache, update_refcount writes
all changed entries to disk. If a refcount block allocation fails, however,
there was no change yet and therefore first_index = last_index = -1. Don't
treat -1 as a normal sector index (resulting in a 512 byte write!) but return
without updating anything in this case.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow2-refcount.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
Stefan Hajnoczi - May 28, 2010, 3:34 p.m.
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

Patch

diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 5b7cda4..22b0b45 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -417,6 +417,10 @@  static int write_refcount_block_entries(BlockDriverState *bs,
         return 0;
     }
 
+    if (first_index < 0) {
+        return 0;
+    }
+
     first_index &= ~(REFCOUNTS_PER_SECTOR - 1);
     last_index = (last_index + REFCOUNTS_PER_SECTOR)
         & ~(REFCOUNTS_PER_SECTOR - 1);