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authorAndrea Parri (Microsoft) <parri.andrea@gmail.com>2020-12-09 08:08:26 +0100
committerWei Liu <wei.liu@kernel.org>2021-02-05 09:55:42 +0000
commite4d221b42354b2e2ddb9187a806afb651eee2cda (patch)
treeed8fb74205a96a8ca8c94eaccb1c8e2eec4ac5db /drivers
parente3fa4b747f085d2cda09bba0533b86fa76038635 (diff)
Drivers: hv: vmbus: Resolve race condition in vmbus_onoffer_rescind()
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 <juvazq@microsoft.com> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com> Reviewed-by: Michael Kelley <mikelley@microsoft.com> Link: https://lore.kernel.org/r/20201209070827.29335-6-parri.andrea@gmail.com Signed-off-by: Wei Liu <wei.liu@kernel.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/hv/channel_mgmt.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 4072fd1f2214..68950a1e4b63 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) {