On Wed, Oct 16, 2019 at 06:50:33AM -0500, Eric Blake wrote:
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.
Yeah, that's workable. So we need virFork() to install a dummy SIGPIPE handler function that is a no-op, *before* it unmasks signals. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|