On Thu, Mar 03, 2011 at 22:09:32 +0800, Daniel Veillard wrote:
This fixes a possible crash of libvirtd during its startup. When qemu driver reconnects to running domains, it iterates over all domain objects in a hash. When reconnecting to an associated qemu monitor fails and the domain is transient, it's immediately removed from the hash. Despite the fact that it's explicitly forbidden to do so. If libvirtd is lucky enough, virHashForEach will access random memory when the callback finishes and the deamon will crash.
Since it's trivial to fix virHashForEach to allow removal of hash entries while iterating through them, I went this way instead of fixing qemuReconnectDomain callback (and possibly others) to avoid deleting the entries.
ACK, removing should be safe then, but adding will still be a big problem due to virHashGrow().
Yeah, that would be a much bigger issue. I pushed the patch.
It's a safety belt, but doesn't replace driving properly. I tend to think we should try to detect reentrant behaviour, for example have a counter increment each time an operation is done on the hash and raise a warning at runtime if the counter changed around iter().
It would probably be easier to set a flag that we're iterating over the hash and let all other APIs fail in that case. Jirka