linux-kernel - Re: [PATCH AUTOSEL 5.11 50/67] Drivers: hv: vmbus: Initialize memory to be sent to the host

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Date:   Wed, 24 Feb 2021 14:16:00 +0100
From:   Andrea Parri <parri.andrea@...il.com>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Juan Vazquez <juvazq@...rosoft.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, linux-hyperv@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 5.11 50/67] Drivers: hv: vmbus: Initialize memory
 to be sent to the host

On Wed, Feb 24, 2021 at 07:50:08AM -0500, Sasha Levin wrote:
> From: "Andrea Parri (Microsoft)" <parri.andrea@...il.com>
> 
> [ Upstream commit e99c4afbee07e9323e9191a20b24d74dbf815bdf ]
> 
> __vmbus_open() and vmbus_teardown_gpadl() do not inizialite the memory
> for the vmbus_channel_open_channel and the vmbus_channel_gpadl_teardown
> objects they allocate respectively.  These objects contain padding bytes
> and fields that are left uninitialized and that are later sent to the
> host, potentially leaking guest data.  Zero initialize such fields to
> avoid leaking sensitive information to the host.
> 
> Reported-by: Juan Vazquez <juvazq@...rosoft.com>
> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@...il.com>
> Reviewed-by: Michael Kelley <mikelley@...rosoft.com>
> Link: https://lore.kernel.org/r/20201209070827.29335-2-parri.andrea@gmail.com
> Signed-off-by: Wei Liu <wei.liu@...nel.org>
> Signed-off-by: Sasha Levin <sashal@...nel.org>

Sasha - This patch is one of a group of patches where a Linux guest running on
Hyper-V will start assuming that hypervisor behavior might be malicious, and
guards against such behavior.  Because this is a new assumption, these patches
are more properly treated as new functionality rather than as bug fixes.  So I
would propose that we *not* bring such patches back to stable branches.

Thanks,
  Andrea


> ---
>  drivers/hv/channel.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
> index 6fb0c76bfbf81..0bd202de79600 100644
> --- a/drivers/hv/channel.c
> +++ b/drivers/hv/channel.c
> @@ -618,7 +618,7 @@ static int __vmbus_open(struct vmbus_channel *newchannel,
>  		goto error_clean_ring;
>  
>  	/* Create and init the channel open message */
> -	open_info = kmalloc(sizeof(*open_info) +
> +	open_info = kzalloc(sizeof(*open_info) +
>  			   sizeof(struct vmbus_channel_open_channel),
>  			   GFP_KERNEL);
>  	if (!open_info) {
> @@ -745,7 +745,7 @@ int vmbus_teardown_gpadl(struct vmbus_channel *channel, u32 gpadl_handle)
>  	unsigned long flags;
>  	int ret;
>  
> -	info = kmalloc(sizeof(*info) +
> +	info = kzalloc(sizeof(*info) +
>  		       sizeof(struct vmbus_channel_gpadl_teardown), GFP_KERNEL);
>  	if (!info)
>  		return -ENOMEM;
> -- 
> 2.27.0
>