Re: [RFC RFT PATCH 1/4] hv: Leak pages if set_memory_encrypted() fails
From: Wei Liu <wei.liu@kernel.org>
Date: 2024-03-01 09:26:41
Also in:
linux-coco, linux-hyperv, lkml
On Wed, Feb 21, 2024 at 06:10:03PM -0800, Rick Edgecombe wrote:
On TDX 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. Hyperv could free decrypted/shared pages if set_memory_encrypted() fails.
"Hyper-V" throughout.
quoted hunk ↗ jump to hunk
Leak the pages if this happens. Only compile tested. Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Wei Liu <wei.liu@kernel.org> Cc: Dexuan Cui <decui@microsoft.com> Cc: linux-hyperv@vger.kernel.org Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> --- drivers/hv/connection.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c index 3cabeeabb1ca..e39493421bbb 100644 --- a/drivers/hv/connection.c +++ b/drivers/hv/connection.c@@ -315,6 +315,7 @@ int vmbus_connect(void) void vmbus_disconnect(void) { + int ret; /* * First send the unload request to the host. */@@ -337,11 +338,13 @@ 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); + ret = set_memory_encrypted((unsigned long)vmbus_connection.monitor_pages[0], 1); + ret |= set_memory_encrypted((unsigned long)vmbus_connection.monitor_pages[1], 1); - hv_free_hyperv_page(vmbus_connection.monitor_pages[0]); - hv_free_hyperv_page(vmbus_connection.monitor_pages[1]); + if (!ret) { + hv_free_hyperv_page(vmbus_connection.monitor_pages[0]); + hv_free_hyperv_page(vmbus_connection.monitor_pages[1]); + }
This silently leaks the pages if set_memory_encrypted() fails. I think there should print some warning or error messages here. Thanks, Wei.
vmbus_connection.monitor_pages[0] = NULL; vmbus_connection.monitor_pages[1] = NULL; } -- 2.34.1