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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>
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2 changed files with 13 additions and 0 deletions
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@ -1063,6 +1063,18 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
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mutex_lock(&vmbus_connection.channel_mutex);
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mutex_lock(&vmbus_connection.channel_mutex);
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channel = relid2channel(rescind->child_relid);
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channel = relid2channel(rescind->child_relid);
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if (channel != NULL) {
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/*
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* Guarantee that no other instance of vmbus_onoffer_rescind()
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* has got a reference to the channel object. Synchronize on
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* &vmbus_connection.channel_mutex.
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*/
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if (channel->rescind_ref) {
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mutex_unlock(&vmbus_connection.channel_mutex);
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return;
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}
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channel->rescind_ref = true;
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}
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mutex_unlock(&vmbus_connection.channel_mutex);
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mutex_unlock(&vmbus_connection.channel_mutex);
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if (channel == NULL) {
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if (channel == NULL) {
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@ -809,6 +809,7 @@ struct vmbus_channel {
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u8 monitor_bit;
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u8 monitor_bit;
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bool rescind; /* got rescind msg */
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bool rescind; /* got rescind msg */
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bool rescind_ref; /* got rescind msg, got channel reference */
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struct completion rescind_event;
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struct completion rescind_event;
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u32 ringbuffer_gpadlhandle;
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u32 ringbuffer_gpadlhandle;
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