From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33223) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gAXnw-0002Zv-44 for qemu-devel@nongnu.org; Thu, 11 Oct 2018 06:02:53 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gAXnt-0006XO-Eo for qemu-devel@nongnu.org; Thu, 11 Oct 2018 06:02:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43186) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gAXnt-0006WY-6X for qemu-devel@nongnu.org; Thu, 11 Oct 2018 06:02:49 -0400 From: Markus Armbruster References: <20181010120841.13214-1-fli@suse.com> <20181010120841.13214-2-fli@suse.com> Date: Thu, 11 Oct 2018 12:02:42 +0200 In-Reply-To: <20181010120841.13214-2-fli@suse.com> (Fei Li's message of "Wed, 10 Oct 2018 20:08:35 +0800") Message-ID: <87in286bst.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH RFC v5 1/7] Fix segmentation fault when qemu_signal_init fails List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Fei Li Cc: qemu-devel@nongnu.org, quintela@redhat.com, dgilbert@redhat.com, peterx@redhat.com, famz@redhat.com Fei Li writes: > Currently, when qemu_signal_init() fails it only returns a non-zero > value but without propagating any Error. But its callers need a > non-null err when runs error_report_err(err), or else 0->msg occurs. The bug is in qemu_init_main_loop(): ret = qemu_signal_init(); if (ret) { return ret; } Fails without setting an error, unlike the other failures. Its callers crash then. > To avoid such segmentation fault, add a new Error parameter to make > the call trace to propagate the err to the final caller. > > Signed-off-by: Fei Li > Reviewed-by: Fam Zheng > --- > include/qemu/osdep.h | 2 +- > util/compatfd.c | 9 ++++++--- > util/main-loop.c | 9 ++++----- > 3 files changed, 11 insertions(+), 9 deletions(-) > > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h > index 4f8559e550..f1f56763a0 100644 > --- a/include/qemu/osdep.h > +++ b/include/qemu/osdep.h > @@ -421,7 +421,7 @@ struct qemu_signalfd_siginfo { > additional fields in the future) */ > }; > > -int qemu_signalfd(const sigset_t *mask); > +int qemu_signalfd(const sigset_t *mask, Error **errp); > void sigaction_invoke(struct sigaction *action, > struct qemu_signalfd_siginfo *info); > #endif > diff --git a/util/compatfd.c b/util/compatfd.c > index 980bd33e52..d3ed890405 100644 > --- a/util/compatfd.c > +++ b/util/compatfd.c > @@ -16,6 +16,7 @@ > #include "qemu/osdep.h" > #include "qemu-common.h" > #include "qemu/thread.h" > +#include "qapi/error.h" > > #include > > @@ -65,7 +66,7 @@ static void *sigwait_compat(void *opaque) > } > } > > -static int qemu_signalfd_compat(const sigset_t *mask) > +static int qemu_signalfd_compat(const sigset_t *mask, Error **errp) > { > struct sigfd_compat_info *info; > QemuThread thread; > @@ -73,11 +74,13 @@ static int qemu_signalfd_compat(const sigset_t *mask) > > info = malloc(sizeof(*info)); > if (info == NULL) { > + error_setg(errp, "Failed to allocate signalfd memory"); > errno = ENOMEM; > return -1; > } > > if (pipe(fds) == -1) { > + error_setg(errp, "Failed to create signalfd pipe"); > free(info); > return -1; > } > @@ -94,7 +97,7 @@ static int qemu_signalfd_compat(const sigset_t *mask) > return fds[0]; > } > > -int qemu_signalfd(const sigset_t *mask) > +int qemu_signalfd(const sigset_t *mask, Error **errp) > { > #if defined(CONFIG_SIGNALFD) > int ret; > @@ -106,5 +109,5 @@ int qemu_signalfd(const sigset_t *mask) > } > #endif > > - return qemu_signalfd_compat(mask); > + return qemu_signalfd_compat(mask, errp); > } I think this takes the Error conversion too far. qemu_signalfd() is like the signalfd() system call, only portable, and setting FD_CLOEXEC. In particular, it reports failure just like a system call: it sets errno and returns -1. I'd prefer to keep it that way. Instead... > diff --git a/util/main-loop.c b/util/main-loop.c > index affe0403c5..9671b6d226 100644 > --- a/util/main-loop.c > +++ b/util/main-loop.c > @@ -71,7 +71,7 @@ static void sigfd_handler(void *opaque) > } > } > > -static int qemu_signal_init(void) > +static int qemu_signal_init(Error **errp) > { > int sigfd; > sigset_t set; > @@ -94,9 +94,8 @@ static int qemu_signal_init(void) > pthread_sigmask(SIG_BLOCK, &set, NULL); > > sigdelset(&set, SIG_IPI); > - sigfd = qemu_signalfd(&set); > + sigfd = qemu_signalfd(&set, errp); > if (sigfd == -1) { > - fprintf(stderr, "failed to create signalfd\n"); > return -errno; > } > ... change this function so: pthread_sigmask(SIG_BLOCK, &set, NULL); sigdelset(&set, SIG_IPI); sigfd = qemu_signalfd(&set); if (sigfd == -1) { - fprintf(stderr, "failed to create signalfd\n"); + error_setg_errno(errp, errno, "failed to create signalfd"); return -errno; } Does this make sense? > @@ -109,7 +108,7 @@ static int qemu_signal_init(void) > > #else /* _WIN32 */ > > -static int qemu_signal_init(void) > +static int qemu_signal_init(Error **errp) > { > return 0; > } > @@ -148,7 +147,7 @@ int qemu_init_main_loop(Error **errp) > > init_clocks(qemu_timer_notify_cb); > > - ret = qemu_signal_init(); > + ret = qemu_signal_init(errp); > if (ret) { > return ret; > }