qcow2: Do not overflow when writing an L1 sector

While writing an L1 table sector, qcow2_write_l1_entry() copies the
respective range from s->l1_table to the local "buf" array. The size of
s->l1_table does not have to be a multiple of L1_ENTRIES_PER_SECTOR;
thus, limit the index which is used for copying all entries to the L1
size.

Cc: qemu-stable@nongnu.org
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit a1391444fe1cfef14976458f3293a2c6945e725c)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 4208dc08b5633153ceb51957bcc0ad3d28f5c125..26827a2746e2ef230e6c2b64ba0bb752b3892b97 100644 (file)
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -158,12 +158,14 @@ static int l2_load(BlockDriverState *bs, uint64_t l2_offset,
 int qcow2_write_l1_entry(BlockDriverState *bs, int l1_index)
 {
     BDRVQcowState *s = bs->opaque;
-    uint64_t buf[L1_ENTRIES_PER_SECTOR];
+    uint64_t buf[L1_ENTRIES_PER_SECTOR] = { 0 };
     int l1_start_index;
     int i, ret;
 
     l1_start_index = l1_index & ~(L1_ENTRIES_PER_SECTOR - 1);
-    for (i = 0; i < L1_ENTRIES_PER_SECTOR; i++) {
+    for (i = 0; i < L1_ENTRIES_PER_SECTOR && l1_start_index + i < s->l1_size;
+         i++)
+    {
         buf[i] = cpu_to_be64(s->l1_table[l1_start_index + i]);
     }