Re: [Qemu-devel] [PATCH 0/3] Remove artificial length limits when parsing options

[Markus Armbruster <armbru@redhat.com>]

Daniel P. Berrangé <berrange@redhat.com> writes:

> A user trying out SMBIOS "OEM strings" feature reported that the data
> they are exposing to the guest was truncated at 1023 bytes, which breaks
> the app consuming in the guest. After searching for the cause I
> eventually found that the QemuOpts parsing is using fixed length 1024
> byte array for option values and 128 byte array for key names.
>
> We can certainly debate whether it is sane to have such long command
> line argument values (it is not sane), but if the OS was capable of
> exec'ing QEMU with such an ARGV array, there is little good reason for
> imposing an artificial length restriction when parsing it. Even worse is
> that we silently truncate without reporting an error when hitting limits
> resulting in a semantically incorrect behaviour, possibly even leading
> to security flaws depending on the data that was truncated.
>
> Thus this patch series removes the artificial length limits by killing
> the fixed length buffers.
>
> Separately I intend to make it possible to read "OEM strings" data from
> a file, to avoid need to have long command line args.

Too bad I haven't been able to complete my quest to kill QemuOpts.

As far as I know, keyval.c's only arbitrary limit is the length of a key
fragment (the things separated by '.').