Re: [libvirt] [PATCH v3] util: Block SIGPIPE until execve in child process

On 10/16/19 4:02 AM, Daniel P. Berrangé wrote: > > The challenge here is that we're in between fork + execve and want signal > handlers back to their defaults at time of execve. > > If we set SIGPIPE to SIG_IGN and then execve() will that get reset back > to SIG_DFL automatically ? Sadly, no. execve() does not change whether a signal is ignored or masked (ignored is more common - a number of CI systems have had issues where the child inherits SIGPIPE ignored because the parent forgot to reset it, but the child wasn't expecting it; but inheriting a signal masked is also a real issue), with the lone exception of SIGCHLD. However, execve() _does_ change a signal that is being caught in the parent into SIG_DFL post-exec. That does mean, however, that it is viable to install a no-op SIGPIPE handler (SIGPIPE is generated but ignored, I/O gets the EPIPE as desired), then post-exec the new process will have SIG_DFL.