On 09/02/2010 04:47 AM, Daniel P. Berrange wrote:
On Wed, Sep 01, 2010 at 05:41:46PM -0400, Cole Robinson wrote:
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 accomodate 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
How about adding a unit test for the virBuffer APIs to verify all this stuff is working as designed. It is nicely self-contained code so we ought to be able to get 100% coverage of all codepaths and error conditions like this one
Daniel
I sent an updated patch with a unittest that reproduces the infinite loop as a start. Thanks, Cole