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The current code will go into an infinite loop if the printf generated string is >= 1000, AND exactly 1 character smaller than the amount of free space in the buffer. When this happens, we are dropped into the loop body, but nothing will actually change, because count == (buf->size - buf->use - 1), and virBufferGrow returns unchanged if count < (buf->size - buf->use) Fix this by removing the '- 1' bit from 'size'. The *nprintf functions handle the NULL byte for us anyways, so we shouldn't need to manually accommodate for it. Here's a bug where we are actually hitting this issue: https://bugzilla.redhat.com/show_bug.cgi?id=602772 v2: Eric's improvements: while -> if (), remove extra va_list variable, make sure we report buffer error if snprintf fails v3: Add tests/virbuftest which reproduces the infinite loop before this patch, works correctly after
LibVirt : simple API for virtualization
Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.
Daniel Veillard <veillard@redhat.com>