diff mbox series

[4/5] qemu-nbd: properly report error if qemu_daemon() is failed

Message ID 20230717145544.194786-5-den@openvz.org (mailing list archive)
State New, archived
Headers show
Series qemu-nbd: fix regression with qemu-nbd --fork run over ssh | expand

Commit Message

Denis V. Lunev July 17, 2023, 2:55 p.m. UTC 
errno has been overwritten by dup2() just below qemu_daemon() and thus
improperly returned to the caller. Fix accordingly.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Eric Blake <eblake@redhat.com>
CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
---
 qemu-nbd.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Comments

Eric Blake July 18, 2023, 5:50 p.m. UTC | #1 
On Mon, Jul 17, 2023 at 04:55:43PM +0200, Denis V. Lunev wrote:
> errno has been overwritten by dup2() just below qemu_daemon() and thus
> improperly returned to the caller. Fix accordingly.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Eric Blake <eblake@redhat.com>
> CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> ---
>  qemu-nbd.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

> 
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index 4450cc826b..f27613cb57 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -932,9 +932,12 @@ int main(int argc, char **argv)
>              error_report("Failed to fork: %s", strerror(errno));
>              exit(EXIT_FAILURE);
>          } else if (pid == 0) {
> +            int saved_errno;
> +
>              close(stderr_fd[0]);
>  
>              ret = qemu_daemon(1, 0);
> +            saved_errno = errno;    /* dup2 will overwrite error below */

I would have written 'may', not 'will'; but that's a triviality not
worth changing.
diff mbox series

Patch

diff --git a/qemu-nbd.c b/qemu-nbd.c
index 4450cc826b..f27613cb57 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -932,9 +932,12 @@  int main(int argc, char **argv)
             error_report("Failed to fork: %s", strerror(errno));
             exit(EXIT_FAILURE);
         } else if (pid == 0) {
+            int saved_errno;
+
             close(stderr_fd[0]);
 
             ret = qemu_daemon(1, 0);
+            saved_errno = errno;    /* dup2 will overwrite error below */
 
             /* Temporarily redirect stderr to the parent's pipe...  */
             if (dup2(stderr_fd[1], STDERR_FILENO) < 0) {
@@ -952,7 +955,7 @@  int main(int argc, char **argv)
             }
 
             if (ret < 0) {
-                error_report("Failed to daemonize: %s", strerror(errno));
+                error_report("Failed to daemonize: %s", strerror(saved_errno));
                 exit(EXIT_FAILURE);
             }