On Fri, Oct 18, 2019 at 05:55:10PM +0800, 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 set SIGPIPE to a dummy no-op handler before unmask signals in > virFork. And there is no need to set SIGPIPE ignored before running > hooks in virExec. At last, set SIGPIPE to defaults before execve. > > Signed-off-by: Wang Yechao <wang.yechao255@xxxxxxxxxx> > --- > v3 patch: > https://www.redhat.com/archives/libvir-list/2019-October/msg00934.html > > Changes in v4: > - don't block SIGPIPE, ignore it when invoke VIR_FORCE_CLOSE and virCommandMassClose > > Changes in v5: > - chang from SIG_IGN to a no-op handler in child process > --- > src/util/vircommand.c | 27 ++++++++++----------------- > 1 file changed, 10 insertions(+), 17 deletions(-) > > diff --git a/src/util/vircommand.c b/src/util/vircommand.c > index 93b3dd2..c13739c 100644 > --- a/src/util/vircommand.c > +++ b/src/util/vircommand.c > @@ -217,6 +217,8 @@ virCommandFDSet(virCommandPtr cmd, > > #ifndef WIN32 > > +static void virDummyHandler(int sig G_GNUC_UNUSED) {} > + > /** > * virFork: > * > @@ -312,6 +314,9 @@ virFork(void) > ignore_value(sigaction(i, &sig_action, NULL)); > } > Put a comment here /* Code that runs between fork & execve might trigger * SIG_PIPE, so we must explicitly set that to a no-op * handler. This handler will get reset to SIG_DFL when * execve() runs */ > + sig_action.sa_handler = virDummyHandler; > + ignore_value(sigaction(SIGPIPE, &sig_action, NULL)); > + > /* Unmask all signals in child, since we've no idea what the > * caller's done with their signal mask and don't want to > * propagate that to children */ > @@ -550,7 +555,7 @@ virExec(virCommandPtr cmd) > g_autofree char *binarystr = NULL; > const char *binary = NULL; > int ret; > - struct sigaction waxon, waxoff; > + struct sigaction sig_action; > g_autofree gid_t *groups = NULL; > int ngroups; > > @@ -718,21 +723,6 @@ virExec(virCommandPtr cmd) > } > } > > - /* virFork reset all signal handlers to the defaults. > - * This is good for the child process, but our hook > - * risks running something that generates SIGPIPE, > - * so we need to temporarily block that again > - */ > - memset(&waxoff, 0, sizeof(waxoff)); > - waxoff.sa_handler = SIG_IGN; > - sigemptyset(&waxoff.sa_mask); > - memset(&waxon, 0, sizeof(waxon)); > - if (sigaction(SIGPIPE, &waxoff, &waxon) < 0) { > - virReportSystemError(errno, "%s", > - _("Could not disable SIGPIPE")); > - goto fork_error; > - } > - > if (virProcessSetMaxMemLock(0, cmd->maxMemLock) < 0) > goto fork_error; > if (virProcessSetMaxProcesses(0, cmd->maxProcesses) < 0) > @@ -783,7 +773,10 @@ virExec(virCommandPtr cmd) > if (virCommandHandshakeChild(cmd) < 0) > goto fork_error; > > - if (sigaction(SIGPIPE, &waxon, NULL) < 0) { > + memset(&sig_action, 0, sizeof(sig_action)); > + sig_action.sa_handler = SIG_DFL; > + sigemptyset(&sig_action.sa_mask); > + if (sigaction(SIGPIPE, &sig_action, NULL) < 0) { > virReportSystemError(errno, "%s", > _("Could not re-enable SIGPIPE")); > goto fork_error; We can just delete this sigaction() call entirely. The execve() call will purge the no-op handler function we registered in virFork(), resetting it back to SIG_DFL, so no need todo it manually here. 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 :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
