2021-08-20 07:56:48

by Xianting Tian

Subject: [RESEND][PATCH] virtio_console: protect max_nr_ports to avoid invalid value

In theory untrusted remote host can pass a big or overflow value
of max_nr_ports to guest, it may cause guest system consumes
a lot of memory when create vqs and other impacts.

Add the protection to guarantee max_nr_ports to get a safe value.

Signed-off-by: Xianting Tian <[email protected]>
---
drivers/char/virtio_console.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 7eaf303a7..bba985c81 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -29,6 +29,8 @@

#define is_rproc_enabled IS_ENABLED(CONFIG_REMOTEPROC)

+#define MAX_NR_PORTS MAX_NR_HVC_CONSOLES
+
/*
* This is a global struct for storing common data for all the devices
* this driver handles.
@@ -2039,6 +2041,9 @@ static int virtcons_probe(struct virtio_device *vdev)
multiport = true;
}

+ /* limit max_nr_ports to avoid invalid value from untrusted remote host */
+ portdev->max_nr_ports = min_t(u32, portdev->max_nr_ports, MAX_NR_PORTS);
+
err = init_vqs(portdev);
if (err < 0) {
dev_err(&vdev->dev, "Error %d initializing vqs\n", err);
--
2.17.1

2021-08-23 11:59:31

by Xianting Tian

Subject: Re: [RESEND][PATCH] virtio_console: protect max_nr_ports to avoid invalid value

Could I get comments for the patch? thanks

Is the value of  MAX_NR_PORTS accurate?

this fix is similar to below patches, which are megered recently,

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.14-rc7&id=63947b3434f475418b9677a393d025c0962c2cf8
<https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.14-rc7&id=63947b3434f475418b9677a393d025c0962c2cf8>

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.14-rc7&id=82e89ea077b93b3c131fa175b0df3acb5b1d5cdf
<https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.14-rc7&id=82e89ea077b93b3c131fa175b0df3acb5b1d5cdf>

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.14-rc7&id=d00d8da5869a2608e97cfede094dfc5e11462a46
<https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v5.14-rc7&id=d00d8da5869a2608e97cfede094dfc5e11462a46>


在 2021/8/20 下午3:52, Xianting Tian 写道:
> In theory untrusted remote host can pass a big or overflow value
> of max_nr_ports to guest, it may cause guest system consumes
> a lot of memory when create vqs and other impacts.
>
> Add the protection to guarantee max_nr_ports to get a safe value.
>
> Signed-off-by: Xianting Tian <[email protected]>
> ---
> drivers/char/virtio_console.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index 7eaf303a7..bba985c81 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -29,6 +29,8 @@
>
> #define is_rproc_enabled IS_ENABLED(CONFIG_REMOTEPROC)
>
> +#define MAX_NR_PORTS MAX_NR_HVC_CONSOLES
> +
> /*
> * This is a global struct for storing common data for all the devices
> * this driver handles.
> @@ -2039,6 +2041,9 @@ static int virtcons_probe(struct virtio_device *vdev)
> multiport = true;
> }
>
> + /* limit max_nr_ports to avoid invalid value from untrusted remote host */
> + portdev->max_nr_ports = min_t(u32, portdev->max_nr_ports, MAX_NR_PORTS);
> +
> err = init_vqs(portdev);
> if (err < 0) {
> dev_err(&vdev->dev, "Error %d initializing vqs\n", err);

2021-08-27 09:02:57

by Greg Kroah-Hartman

Subject: Re: [RESEND][PATCH] virtio_console: protect max_nr_ports to avoid invalid value

On Fri, Aug 20, 2021 at 03:52:19PM +0800, Xianting Tian wrote:
> In theory untrusted remote host can pass a big or overflow value
> of max_nr_ports to guest, it may cause guest system consumes
> a lot of memory when create vqs and other impacts.

How can you have a untrusted host? Can't they do a lot worse things
than just this?

>
> Add the protection to guarantee max_nr_ports to get a safe value.
>
> Signed-off-by: Xianting Tian <[email protected]>
> ---
> drivers/char/virtio_console.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index 7eaf303a7..bba985c81 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -29,6 +29,8 @@
>
> #define is_rproc_enabled IS_ENABLED(CONFIG_REMOTEPROC)
>
> +#define MAX_NR_PORTS MAX_NR_HVC_CONSOLES

How was this value picked?

thanks,

greg k-h