Commit 44deba5a authored by Kevin Wolf's avatar Kevin Wolf
Browse files

qcow2: Make qiov match request size until backing file EOF 



If a qcow2 image has a shorter backing file and a read request to
unallocated clusters goes across EOF of the backing file, the backing
file sees a shortened request and the rest is filled with zeros.
However, the original too long qiov was used with the shortened request.

This patch makes the qiov size match the request size, avoiding a
potential buffer overflow in raw-posix.

Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
Reviewed-by: default avatarMax Reitz <mreitz@redhat.com>
parent 33f461e0

block/qcow2.c

+10 −1
Original line number Diff line number Diff line
@@ -1020,11 +1020,20 @@ static coroutine_fn int qcow2_co_readv(BlockDriverState *bs, int64_t sector_num, 
                n1 = qcow2_backing_read1(bs->backing_hd, &hd_qiov,

                    sector_num, cur_nr_sectors);

                if (n1 > 0) {

                    QEMUIOVector local_qiov;



                    qemu_iovec_init(&local_qiov, hd_qiov.niov);

                    qemu_iovec_concat(&local_qiov, &hd_qiov, 0,

                                      n1 * BDRV_SECTOR_SIZE);



                    BLKDBG_EVENT(bs->file, BLKDBG_READ_BACKING_AIO);

                    qemu_co_mutex_unlock(&s->lock);

                    ret = bdrv_co_readv(bs->backing_hd, sector_num,

                                        n1, &hd_qiov);

                                        n1, &local_qiov);

                    qemu_co_mutex_lock(&s->lock);



                    qemu_iovec_destroy(&local_qiov);



                    if (ret < 0) {

                        goto fail;

                    }