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Message-ID: <20201202122254.zjhu3cfcq3zwvmvu@liuwe-devbox-debian-v2>
Date: Wed, 2 Dec 2020 12:22:54 +0000
From: Wei Liu <wei.liu@...nel.org>
To: "Andrea Parri (Microsoft)" <parri.andrea@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org,
"K . Y . Srinivasan" <kys@...rosoft.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Stephen Hemminger <sthemmin@...rosoft.com>,
Wei Liu <wei.liu@...nel.org>,
Michael Kelley <mikelley@...rosoft.com>,
Juan Vazquez <juvazq@...rosoft.com>,
Saruhan Karademir <skarade@...rosoft.com>
Subject: Re: [PATCH v2 2/7] Drivers: hv: vmbus: Avoid double fetch of msgtype
in vmbus_on_msg_dpc()
On Wed, Dec 02, 2020 at 10:22:09AM +0100, Andrea Parri (Microsoft) wrote:
> vmbus_on_msg_dpc() double fetches from msgtype. The double fetch can
> lead to an out-of-bound access when accessing the channel_message_table
> array. In turn, the use of the out-of-bound entry could lead to code
> execution primitive (entry->message_handler()). Avoid the double fetch
> by saving the value of msgtype into a local variable.
>
> Reported-by: Juan Vazquez <juvazq@...rosoft.com>
> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@...il.com>
> ---
> drivers/hv/vmbus_drv.c | 18 +++++++++++++-----
> 1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 0a2711aa63a15..82b23baa446d7 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -1057,6 +1057,7 @@ void vmbus_on_msg_dpc(unsigned long data)
> struct hv_message *msg = (struct hv_message *)page_addr +
> VMBUS_MESSAGE_SINT;
> struct vmbus_channel_message_header *hdr;
> + enum vmbus_channel_message_type msgtype;
> const struct vmbus_channel_message_table_entry *entry;
> struct onmessage_work_context *ctx;
> u32 message_type = msg->header.message_type;
> @@ -1072,12 +1073,19 @@ void vmbus_on_msg_dpc(unsigned long data)
> /* no msg */
> return;
>
> + /*
> + * The hv_message object is in memory shared with the host. The host
> + * could erroneously or maliciously modify such object. Make sure to
> + * validate its fields and avoid double fetches whenever feasible.
> + */
> +
> hdr = (struct vmbus_channel_message_header *)msg->u.payload;
> + msgtype = hdr->msgtype;
Should READ_ONCE be used here?
Wei.
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