Re: [PATCH AUTOSEL 4.19 21/26] Drivers: hv: vmbus: Resolve race condition in vmbus_onoffer_rescind()
From: Andrea Parri <parri.andrea@gmail.com>
Date: 2021-02-24 14:42:20
Also in:
linux-hyperv, lkml
On Wed, Feb 24, 2021 at 07:54:29AM -0500, Sasha Levin wrote:
From: "Andrea Parri (Microsoft)" <parri.andrea@gmail.com> [ 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 <redacted> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com> Reviewed-by: Michael Kelley <redacted> Link: https://lore.kernel.org/r/20201209070827.29335-6-parri.andrea@gmail.com (local) Signed-off-by: Wei Liu <wei.liu@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
Same here. Andrea
quoted hunk ↗ jump to hunk
--- 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(&vmbus_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 + * &vmbus_connection.channel_mutex. + */ + if (channel->rescind_ref) { + mutex_unlock(&vmbus_connection.channel_mutex); + return; + } + channel->rescind_ref = true; + } mutex_unlock(&vmbus_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