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[95.239.64.30]) by smtp.gmail.com with ESMTPSA id e27sm1535936wrc.9.2020.12.02.01.22.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Dec 2020 01:22:49 -0800 (PST) From: "Andrea Parri (Microsoft)" To: linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org Cc: "K . Y . Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , Michael Kelley , Juan Vazquez , Saruhan Karademir , "Andrea Parri (Microsoft)" Subject: [PATCH v2 6/7] Drivers: hv: vmbus: Resolve race condition in vmbus_onoffer_rescind() Date: Wed, 2 Dec 2020 10:22:13 +0100 Message-Id: <20201202092214.13520-7-parri.andrea@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201202092214.13520-1-parri.andrea@gmail.com> References: <20201202092214.13520-1-parri.andrea@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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) --- 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 4072fd1f22146..68950a1e4b638 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -1063,6 +1063,18 @@ 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 2ea967bc17adf..f0d48a368f131 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -809,6 +809,7 @@ 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; -- 2.25.1