[PATCH AUTOSEL 6.1 17/19] uio_hv_generic: Don't free decrypted memory

[Sasha Levin]

From: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>

[ Upstream commit 3d788b2fbe6a1a1a9e3db09742b90809d51638b7 ]

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@xxxxxxxxx>
Signed-off-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240311161558.1310-5-mhklinux@xxxxxxxxxxx
Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
Message-ID: <20240311161558.1310-5-mhklinux@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 c08a6cfd119f2..e5789dfcaff61 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;
 	}
 
-- 
2.43.0