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

On 10/15/19 9:43 PM, Eric Blake wrote: > On 10/15/19 9:25 PM, Wang Yechao wrote: > > Libvirtd has set SIGPIPE to ignored, and virFork resets all signal > > handlers to the defaults. But child process may write logs to > > stderr/stdout, that may generate SIGPIPE if journald has stopped. > > > > So block SIGPIPE in virFork, and unblock it before execve. > > How does that help?  If writing to stderr hits EOF, it will queue up a > SIGPIPE to be delivered as soon as you unblock SIGPIPE. > > The correct fix is to not unblock SIGPIPE until after any point at which > you would be performing I/O that must not fail due to SIGPIPE, rather > than messing with signal masks to just delay when SIGPIPE is delivered. Let's word this better: The correct fix is to keep SIGPIPE ignored until after any point at which you would be performing I/O that must not cause SIGPIPE, reverting SIGPIPE back to SIG_DFL at the last possible moment. Messing with signal masks merely delays when SIGPIPE is delivered, rather than avoiding it.