netdev - [PATCH v2 4/5] uio_hv_generic: Don't free decrypted memory

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Message-Id: <20240311161558.1310-5-mhklinux@outlook.com>
Date: Mon, 11 Mar 2024 09:15:57 -0700
From: mhkelley58@...il.com
To: rick.p.edgecombe@...el.com,
	kys@...rosoft.com,
	haiyangz@...rosoft.com,
	wei.liu@...nel.org,
	decui@...rosoft.com,
	gregkh@...uxfoundation.org,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	kirill.shutemov@...ux.intel.com,
	dave.hansen@...ux.intel.com,
	linux-kernel@...r.kernel.org,
	linux-hyperv@...r.kernel.org,
	netdev@...r.kernel.org,
	linux-coco@...ts.linux.dev
Cc: sathyanarayanan.kuppuswamy@...ux.intel.com,
	elena.reshetova@...el.com
Subject: [PATCH v2 4/5] uio_hv_generic: Don't free decrypted memory

From: Rick Edgecombe <rick.p.edgecombe@...el.com>

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.

The VMBus device UIO driver could free decrypted/shared pages if
set_memory_decrypted() fails. Check the decrypted field in the gpadl
to decide whether to free the memory.

Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
Signed-off-by: Michael Kelley <mhklinux@...look.com>
---
 drivers/uio/uio_hv_generic.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index 20d9762331bd..6be3462b109f 100644
--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c
@@ -181,12 +181,14 @@ hv_uio_cleanup(struct hv_device *dev, struct hv_uio_private_data *pdata)
 {
 	if (pdata->send_gpadl.gpadl_handle) {
 		vmbus_teardown_gpadl(dev->channel, &pdata->send_gpadl);
-		vfree(pdata->send_buf);
+		if (!pdata->send_gpadl.decrypted)
+			vfree(pdata->send_buf);
 	}
 
 	if (pdata->recv_gpadl.gpadl_handle) {
 		vmbus_teardown_gpadl(dev->channel, &pdata->recv_gpadl);
-		vfree(pdata->recv_buf);
+		if (!pdata->recv_gpadl.decrypted)
+			vfree(pdata->recv_buf);
 	}
 }
 
@@ -295,7 +297,8 @@ hv_uio_probe(struct hv_device *dev,
 	ret = vmbus_establish_gpadl(channel, pdata->recv_buf,
 				    RECV_BUFFER_SIZE, &pdata->recv_gpadl);
 	if (ret) {
-		vfree(pdata->recv_buf);
+		if (!pdata->recv_gpadl.decrypted)
+			vfree(pdata->recv_buf);
 		goto fail_close;
 	}
 
@@ -317,7 +320,8 @@ hv_uio_probe(struct hv_device *dev,
 	ret = vmbus_establish_gpadl(channel, pdata->send_buf,
 				    SEND_BUFFER_SIZE, &pdata->send_gpadl);
 	if (ret) {
-		vfree(pdata->send_buf);
+		if (!pdata->send_gpadl.decrypted)
+			vfree(pdata->send_buf);
 		goto fail_close;
 	}
 
-- 
2.25.1