On Thu, Nov 11, 2021 at 7:36 PM Roman Kagan <rvkagan@yandex-team.ru> wrote:

> After the return from tcp_chr_recv, tcp_chr_sync_read calls into a
> function which eventually makes a system call and may clobber errno.
>
> Make a copy of errno right after tcp_chr_recv and restore the errno on
> return from tcp_chr_sync_read.
>
> Signed-off-by: Roman Kagan <rvkagan@yandex-team.ru>
>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

---
>  chardev/char-socket.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/chardev/char-socket.c b/chardev/char-socket.c
> index 90054ce58c..cf7f2ba65a 100644
> --- a/chardev/char-socket.c
> +++ b/chardev/char-socket.c
> @@ -581,6 +581,7 @@ static int tcp_chr_sync_read(Chardev *chr, const
> uint8_t *buf, int len)
>  {
>      SocketChardev *s = SOCKET_CHARDEV(chr);
>      int size;
> +    int saved_errno;
>
>      if (s->state != TCP_CHARDEV_STATE_CONNECTED) {
>          return 0;
> @@ -588,6 +589,7 @@ static int tcp_chr_sync_read(Chardev *chr, const
> uint8_t *buf, int len)
>
>      qio_channel_set_blocking(s->ioc, true, NULL);
>      size = tcp_chr_recv(chr, (void *) buf, len);
> +    saved_errno = errno;
>      if (s->state != TCP_CHARDEV_STATE_DISCONNECTED) {
>          qio_channel_set_blocking(s->ioc, false, NULL);
>      }
> @@ -596,6 +598,7 @@ static int tcp_chr_sync_read(Chardev *chr, const
> uint8_t *buf, int len)
>          tcp_chr_disconnect(chr);
>      }
>
> +    errno = saved_errno;
>      return size;
>  }
>
> --
> 2.33.1
>
>
>

-- 
Marc-André Lureau