Re: [PATCH 1/4] chardev: fix qemu_chr_open_fd() being called with fd=-1

From: "Daniel P. Berrangé" <berrange@redhat.com>
To: marcandre.lureau@redhat.com
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Subject: Re: [PATCH 1/4] chardev: fix qemu_chr_open_fd() being called with fd=-1
Date: Tue, 3 Aug 2021 09:40:41 +0100	[thread overview]
Message-ID: <YQkBCUCoXpHR8cZ6@redhat.com> (raw)
In-Reply-To: <20210723102825.1790112-2-marcandre.lureau@redhat.com>

On Fri, Jul 23, 2021 at 02:28:22PM +0400, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> The "file" chardev may call qemu_chr_open_fd() with fd_in=-1. This may
> cause invalid system calls, as the QIOChannel is assumed to be properly
> initialized later on.
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  chardev/char-fd.c | 22 +++++++++++++---------
>  1 file changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/chardev/char-fd.c b/chardev/char-fd.c
> index 1cd62f2779..ee85a52c06 100644
> --- a/chardev/char-fd.c
> +++ b/chardev/char-fd.c
> @@ -133,15 +133,19 @@ void qemu_chr_open_fd(Chardev *chr,
>      FDChardev *s = FD_CHARDEV(chr);
>      char *name;
>  
> -    s->ioc_in = QIO_CHANNEL(qio_channel_file_new_fd(fd_in));
> -    name = g_strdup_printf("chardev-file-in-%s", chr->label);
> -    qio_channel_set_name(QIO_CHANNEL(s->ioc_in), name);
> -    g_free(name);
> -    s->ioc_out = QIO_CHANNEL(qio_channel_file_new_fd(fd_out));
> -    name = g_strdup_printf("chardev-file-out-%s", chr->label);
> -    qio_channel_set_name(QIO_CHANNEL(s->ioc_out), name);
> -    g_free(name);
> -    qemu_set_nonblock(fd_out);
> +    if (fd_in >= 0) {
> +        s->ioc_in = QIO_CHANNEL(qio_channel_file_new_fd(fd_in));
> +        name = g_strdup_printf("chardev-file-in-%s", chr->label);
> +        qio_channel_set_name(QIO_CHANNEL(s->ioc_in), name);
> +        g_free(name);
> +    }
> +    if (fd_out >= 0) {
> +        s->ioc_out = QIO_CHANNEL(qio_channel_file_new_fd(fd_out));
> +        name = g_strdup_printf("chardev-file-out-%s", chr->label);
> +        qio_channel_set_name(QIO_CHANNEL(s->ioc_out), name);
> +        g_free(name);
> +        qemu_set_nonblock(fd_out);
> +    }

Other code in this file assumes ioc_out is non-NULL, so this looks
like an incomplete fix.

Regards,
Daniel
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