On 1/15/19 10:26 AM, Vladimir Sementsov-Ogievskiy wrote: >>> @size is not size of the image, but size of the export, so it may be less >>> than dev_offset >>> (qemu-nbd.c do "fd_size -= dev_offset" before "nbd_export_new(bs, >>> dev_offset, fd_size, " >> >> But the assert is fine because patch 3/19 fixed qemu-nbd.c to never pass >> in dev_offset larger than size (it fails up front if dev_offset is out >> of bounds, whether from the -o command line option or from what it read >> from the partition header with the -P command line option). >> > > Don't follow =( > > Assume, image size 3M, and we have offset 2M, i.e. -o 2M. > > than in qemu-nbd.c, we have > > fd_size = blk_getlength(blk); # 3M > ... > fd_size -= dev_offset; # 1M > ... > export = nbd_export_new(bs, dev_offset, fd_size # bs, 2M, 1M > > in nbd_export_new: > > assert(dev_offset <= size); # 2M <= 1M > > fail.
Ouch, you are right. I don't need the assertion in server.c at all; because all callers pass in a validated size, but the validated size has no comparable relation to dev_offset. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
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