Re: [Qemu-devel] [PATCH] qapi: change QmpInputVisitor to QSLIST

[Paolo Bonzini]

On 07/07/2016 10:19, Markus Armbruster wrote:
> Actually, you should either prove that untrusted input still cannot make
> us allocated unbounded amounts of memory, or bring the limit right back.

This is not where untrusted input can be blocked from allocating
unbounded memory---that would be QmpOutputVisitor, which converts a
stream of visitor calls into a QObject.

The QmpInputVisitor's allocation depth is bounded by the number of
levels in the incoming QObject, so a QmpInputVisitor cannot allocate
more memory than whatever has been allocated already by QEMU.

In addition, QmpOutputVisitor allocates memory not just for the stack
but also a QObject for every *value*.  So you can make QmpOutputVisitor
allocate unbounded memory even with a single huge QDict.

Paolo