Re: [PATCH AUTOSEL 4.19 21/26] Drivers: hv: vmbus: Resolve race condition in vmbus_onoffer_rescind()
On Wed, Feb 24, 2021 at 07:54:29AM -0500, Sasha Levin wrote:
> From: "Andrea Parri (Microsoft)"
>
> [ Upstream commit e4d221b42354b2e2ddb9187a806afb651eee2cda ]
>
> An erroneous or malicious host could send multiple rescind messages for
> a same channel. In vmbus_onoffer_rescind(), the guest maps the channel
> ID to obtain a pointer to the channel object and it eventually releases
> such object and associated data. The host could time rescind messages
> and lead to an use-after-free. Add a new flag to the channel structure
> to make sure that only one instance of vmbus_onoffer_rescind() can get
> the reference to the channel object.
>
> Reported-by: Juan Vazquez
> Signed-off-by: Andrea Parri (Microsoft)
> Reviewed-by: Michael Kelley
> Link: https://lore.kernel.org/r/20201209070827.29335-6-parri.and...@gmail.com
> Signed-off-by: Wei Liu
> Signed-off-by: Sasha Levin
Same here.
Andrea
> ---
> drivers/hv/channel_mgmt.c | 12
> include/linux/hyperv.h| 1 +
> 2 files changed, 13 insertions(+)
>
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index 7920b0d7e35a7..1322e799938af 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -954,6 +954,18 @@ static void vmbus_onoffer_rescind(struct
> vmbus_channel_message_header *hdr)
>
> mutex_lock(_connection.channel_mutex);
> channel = relid2channel(rescind->child_relid);
> + if (channel != NULL) {
> + /*
> + * Guarantee that no other instance of vmbus_onoffer_rescind()
> + * has got a reference to the channel object. Synchronize on
> + * _connection.channel_mutex.
> + */
> + if (channel->rescind_ref) {
> + mutex_unlock(_connection.channel_mutex);
> + return;
> + }
> + channel->rescind_ref = true;
> + }
> mutex_unlock(_connection.channel_mutex);
>
> if (channel == NULL) {
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index 35461d49d3aee..59525fe25abde 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -736,6 +736,7 @@ struct vmbus_channel {
> u8 monitor_bit;
>
> bool rescind; /* got rescind msg */
> + bool rescind_ref; /* got rescind msg, got channel reference */
> struct completion rescind_event;
>
> u32 ringbuffer_gpadlhandle;
> --
> 2.27.0
>
[PATCH AUTOSEL 4.19 21/26] Drivers: hv: vmbus: Resolve race condition in vmbus_onoffer_rescind()
From: "Andrea Parri (Microsoft)"
[ Upstream commit e4d221b42354b2e2ddb9187a806afb651eee2cda ]
An erroneous or malicious host could send multiple rescind messages for
a same channel. In vmbus_onoffer_rescind(), the guest maps the channel
ID to obtain a pointer to the channel object and it eventually releases
such object and associated data. The host could time rescind messages
and lead to an use-after-free. Add a new flag to the channel structure
to make sure that only one instance of vmbus_onoffer_rescind() can get
the reference to the channel object.
Reported-by: Juan Vazquez
Signed-off-by: Andrea Parri (Microsoft)
Reviewed-by: Michael Kelley
Link: https://lore.kernel.org/r/20201209070827.29335-6-parri.and...@gmail.com
Signed-off-by: Wei Liu
Signed-off-by: Sasha Levin
---
drivers/hv/channel_mgmt.c | 12
include/linux/hyperv.h| 1 +
2 files changed, 13 insertions(+)
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 7920b0d7e35a7..1322e799938af 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -954,6 +954,18 @@ static void vmbus_onoffer_rescind(struct
vmbus_channel_message_header *hdr)
mutex_lock(_connection.channel_mutex);
channel = relid2channel(rescind->child_relid);
+ if (channel != NULL) {
+ /*
+* Guarantee that no other instance of vmbus_onoffer_rescind()
+* has got a reference to the channel object. Synchronize on
+* _connection.channel_mutex.
+*/
+ if (channel->rescind_ref) {
+ mutex_unlock(_connection.channel_mutex);
+ return;
+ }
+ channel->rescind_ref = true;
+ }
mutex_unlock(_connection.channel_mutex);
if (channel == NULL) {
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 35461d49d3aee..59525fe25abde 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -736,6 +736,7 @@ struct vmbus_channel {
u8 monitor_bit;
bool rescind; /* got rescind msg */
+ bool rescind_ref; /* got rescind msg, got channel reference */
struct completion rescind_event;
u32 ringbuffer_gpadlhandle;
--
2.27.0
