Drivers: hv: vmbus: Leak pages if set_memory_encrypted() fails

[ Upstream commit 03f5a999adba062456c8c818a683beb1b498983a ]

In CoCo VMs it is possible for the untrusted host to cause
set_memory_encrypted() or set_memory_decrypted() to fail such that an
error is returned and the resulting memory is shared. Callers need to
take care to handle these errors to avoid returning decrypted (shared)
memory to the page allocator, which could lead to functional or security
issues.

VMBus code could free decrypted pages if set_memory_encrypted()/decrypted()
fails. Leak the pages if this happens.

Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/r/20240311161558.1310-2-mhklinux@outlook.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20240311161558.1310-2-mhklinux@outlook.com>
Stable-dep-of: 09eea7ad0b8e ("Drivers: hv: Allocate interrupt and monitor pages aligned to system page boundary")
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index ebf15f31d97e3018475416121d21ec1c923c27f3..744d2809acc3fb531721f269d91e006c5bad7e23 100644 (file)
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -236,8 +236,17 @@ int vmbus_connect(void)
                                vmbus_connection.monitor_pages[0], 1);
        ret |= set_memory_decrypted((unsigned long)
                                vmbus_connection.monitor_pages[1], 1);
-       if (ret)
+       if (ret) {
+               /*
+                * If set_memory_decrypted() fails, the encryption state
+                * of the memory is unknown. So leak the memory instead
+                * of risking returning decrypted memory to the free list.
+                * For simplicity, always handle both pages the same.
+                */
+               vmbus_connection.monitor_pages[0] = NULL;
+               vmbus_connection.monitor_pages[1] = NULL;
                goto cleanup;
+       }
 
        /*
         * Set_memory_decrypted() will change the memory contents if
@@ -336,13 +345,19 @@ void vmbus_disconnect(void)
                vmbus_connection.int_page = NULL;
        }
 
-       set_memory_encrypted((unsigned long)vmbus_connection.monitor_pages[0], 1);
-       set_memory_encrypted((unsigned long)vmbus_connection.monitor_pages[1], 1);
+       if (vmbus_connection.monitor_pages[0]) {
+               if (!set_memory_encrypted(
+                       (unsigned long)vmbus_connection.monitor_pages[0], 1))
+                       hv_free_hyperv_page(vmbus_connection.monitor_pages[0]);
+               vmbus_connection.monitor_pages[0] = NULL;
+       }
 
-       hv_free_hyperv_page(vmbus_connection.monitor_pages[0]);
-       hv_free_hyperv_page(vmbus_connection.monitor_pages[1]);
-       vmbus_connection.monitor_pages[0] = NULL;
-       vmbus_connection.monitor_pages[1] = NULL;
+       if (vmbus_connection.monitor_pages[1]) {
+               if (!set_memory_encrypted(
+                       (unsigned long)vmbus_connection.monitor_pages[1], 1))
+                       hv_free_hyperv_page(vmbus_connection.monitor_pages[1]);
+               vmbus_connection.monitor_pages[1] = NULL;
+       }
 }
 
 /*