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[1/2] qcow2: Do not overflow when writing an L1 sector

Message ID 1413465957-20865-2-git-send-email-mreitz@redhat.com
State New
Headers show

Commit Message

Max Reitz Oct. 16, 2014, 1:25 p.m. UTC 
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>
---
 block/qcow2-cluster.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Comments

Peter Lieven Oct. 20, 2014, 6:23 a.m. UTC | #1 
On 16.10.2014 15:25, Max Reitz wrote:
> 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>
> ---
>   block/qcow2-cluster.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
> index f7dd8c0..4d888c7 100644
> --- a/block/qcow2-cluster.c
> +++ b/block/qcow2-cluster.c
> @@ -164,12 +164,14 @@ 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]);
>       }
>   

Reviewed-by: Peter Lieven <pl@kamp.de>
diff mbox

Patch

diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index f7dd8c0..4d888c7 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -164,12 +164,14 @@  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]);
     }