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Re: [Qemu-devel] [PATCH v3 04/13] char: forbid direct chardevice access
From: |
Marc-André Lureau |
Subject: |
Re: [Qemu-devel] [PATCH v3 04/13] char: forbid direct chardevice access for hotswap devices |
Date: |
Wed, 31 May 2017 19:21:15 +0000 |
On Tue, May 30, 2017 at 6:13 PM Anton Nefedov <address@hidden>
wrote:
> qemu_chr_fe_get_driver() is unsafe, frontends with hotswap support
> should not access CharDriver ptr directly as CharDriver might change.
>
> Signed-off-by: Anton Nefedov <address@hidden>
> Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
>
Reviewed-by: Marc-André Lureau <address@hidden>
> ---
> chardev/char.c | 7 +++++++
> include/sysemu/char.h | 10 ++++++++++
> 2 files changed, 17 insertions(+)
>
> diff --git a/chardev/char.c b/chardev/char.c
> index ba1a5f5..1eed934 100644
> --- a/chardev/char.c
> +++ b/chardev/char.c
> @@ -484,9 +484,16 @@ static Notifier muxes_realize_notify = {
>
> Chardev *qemu_chr_fe_get_driver(CharBackend *be)
> {
> + /* this is unsafe for the users that support chardev hotswap */
> + assert(be->chr_be_change == NULL);
> return be->chr;
> }
>
> +bool qemu_chr_fe_backend_connected(CharBackend *be)
> +{
> + return !!be->chr;
> +}
> +
> static bool qemu_chr_fe_connect(CharBackend *b, Chardev *s, Error **errp)
> {
> int tag = 0;
> diff --git a/include/sysemu/char.h b/include/sysemu/char.h
> index 014ebbc..117d628 100644
> --- a/include/sysemu/char.h
> +++ b/include/sysemu/char.h
> @@ -391,10 +391,20 @@ bool qemu_chr_fe_init(CharBackend *b, Chardev *s,
> Error **errp);
> *
> * Returns the driver associated with a CharBackend or NULL if no
> * associated Chardev.
> + * Note: avoid this function as the driver should never be accessed
> directly,
> + * especially by the frontends that support chardevice hotswap.
> + * Consider qemu_chr_fe_backend_connected() to check for driver
> existence
> */
> Chardev *qemu_chr_fe_get_driver(CharBackend *be);
>
> /**
> + * @qemu_chr_fe_backend_connected:
> + *
> + * Returns true if there is a chardevice associated with @be.
> + */
> +bool qemu_chr_fe_backend_connected(CharBackend *be);
> +
> +/**
> * @qemu_chr_fe_deinit:
> *
> * Dissociate the CharBackend from the Chardev.
> --
> 2.7.4
>
>
> --
Marc-André Lureau
- [Qemu-devel] [PATCH v3 00/13] chardevice hotswap, Anton Nefedov, 2017/05/30
- [Qemu-devel] [PATCH v3 01/13] char: move QemuOpts->ChardevBackend translation to a separate func, Anton Nefedov, 2017/05/30
- [Qemu-devel] [PATCH v3 02/13] char: add backend hotswap handler, Anton Nefedov, 2017/05/30
- [Qemu-devel] [PATCH v3 03/13] char: chardevice hotswap, Anton Nefedov, 2017/05/30
- [Qemu-devel] [PATCH v3 04/13] char: forbid direct chardevice access for hotswap devices, Anton Nefedov, 2017/05/30
- Re: [Qemu-devel] [PATCH v3 04/13] char: forbid direct chardevice access for hotswap devices,
Marc-André Lureau <=
- [Qemu-devel] [PATCH v3 05/13] char: avoid chardevice direct access, Anton Nefedov, 2017/05/30
- [Qemu-devel] [PATCH v3 06/13] test-char: unref chardev-udp after test, Anton Nefedov, 2017/05/30
- [Qemu-devel] [PATCH v3 09/13] test-char: add hotswap test, Anton Nefedov, 2017/05/30
- [Qemu-devel] [PATCH v3 07/13] test-char: split char_udp_test, Anton Nefedov, 2017/05/30
- [Qemu-devel] [PATCH v3 08/13] test-char: split char_file_test, Anton Nefedov, 2017/05/30