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Re: [Qemu-devel] [PATCH RFC v5 1/7] Fix segmentation fault when qemu_sig
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] [PATCH RFC v5 1/7] Fix segmentation fault when qemu_signal_init fails |
Date: |
Thu, 11 Oct 2018 12:02:42 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) |
Fei Li <address@hidden> 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 <address@hidden>
> Reviewed-by: Fam Zheng <address@hidden>
> ---
> 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 <sys/syscall.h>
>
> @@ -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;
> }
- [Qemu-devel] [PATCH RFC v5 0/7] qemu_thread_create: propagate errors to callers to check, Fei Li, 2018/10/10
- [Qemu-devel] [PATCH RFC v5 1/7] Fix segmentation fault when qemu_signal_init fails, Fei Li, 2018/10/10
- Re: [Qemu-devel] [PATCH RFC v5 1/7] Fix segmentation fault when qemu_signal_init fails,
Markus Armbruster <=
- Re: [Qemu-devel] [PATCH RFC v5 1/7] Fix segmentation fault when qemu_signal_init fails, Fei Li, 2018/10/12
- Re: [Qemu-devel] [PATCH RFC v5 1/7] Fix segmentation fault when qemu_signal_init fails, Markus Armbruster, 2018/10/12
- Re: [Qemu-devel] [PATCH RFC v5 1/7] Fix segmentation fault when qemu_signal_init fails, Fei Li, 2018/10/12
- Re: [Qemu-devel] [PATCH RFC v5 1/7] Fix segmentation fault when qemu_signal_init fails, Markus Armbruster, 2018/10/12
- Re: [Qemu-devel] [PATCH RFC v5 1/7] Fix segmentation fault when qemu_signal_init fails, Fei Li, 2018/10/17
- Re: [Qemu-devel] [PATCH RFC v5 1/7] Fix segmentation fault when qemu_signal_init fails, Fei Li, 2018/10/18
[Qemu-devel] [PATCH RFC v5 2/7] ui/vnc.c: polish vnc_init_func, Fei Li, 2018/10/10