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

> On Mon, Apr 16, 2018 at 06:30:45PM +0200, Markus Armbruster wrote:
>> Daniel P. Berrangé <berra...@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 '.').
> Looks like that's the same scenario I tried to address in patch 2. The
> 'key' part in QemuOpts has the same 128 byte limit as in the keyval.c
> code. I fear that could be hit with -blockdev when setting params on
> very deeply nested block backends.  On the plus side  keyval.c actually
> reports an error when it hits its 128 byte limit, instead of silently
> carrying on as if all was well like QemuOpts did :-)

In keyval.c, the key (things like "a.b.c") can be arbitrarily long
(well, until g_malloc() throws in the towel), but each key fragment
("a", "b" and "c") is limited to 128 bytes.

If key length was limited there, I would've asked you to fix it there,

Reply via email to