linux-kernel - [PATCH] virt/coco/sev-guest: Don't free decrypted memory

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Date: Fri, 14 Jun 2024 13:10:36 +0800
From: Li RongQing <lirongqing@...du.com>
To: thomas.lendacky@....com,
	dan.j.williams@...el.com,
	bp@...en8.de,
	linux-kernel@...r.kernel.org
Cc: Li RongQing <lirongqing@...du.com>
Subject: [PATCH] virt/coco/sev-guest: Don't free decrypted memory

In CoCo VMs, it is possible for the untrusted host to cause
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. so don't free decrypted memory

Signed-off-by: Li RongQing <lirongqing@...du.com>
---
 drivers/virt/coco/sev-guest/sev-guest.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 654290a8e..799563a 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -730,8 +730,7 @@ static void *alloc_shared_pages(struct device *dev, size_t sz)
 
 	ret = set_memory_decrypted((unsigned long)page_address(page), npages);
 	if (ret) {
-		dev_err(dev, "failed to mark page shared, ret=%d\n", ret);
-		__free_pages(page, get_order(sz));
+		dev_err(dev, "failed to mark page shared, leak page, ret=%d\n", ret);
 		return NULL;
 	}
 
-- 
2.9.4