Re: [libvirt] [PATCH] util: Allow removing hash entries in virHashForEach

> 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().

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().