[tip: x86/urgent] virt: tdx-guest: Just leak decrypted memory on unrecoverable errors

[tip-bot2 for Li RongQing]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     10331a93486ffb7b85ceea9da48a37da8cc16bdf
Gitweb:        https://git.kernel.org/tip/10331a93486ffb7b85ceea9da48a37da8cc16bdf
Author:        Li RongQing <lirongqing@xxxxxxxxx>
AuthorDate:    Wed, 19 Jun 2024 19:18:01 +08:00
Committer:     Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Wed, 18 Dec 2024 06:07:55 -08:00

virt: tdx-guest: Just leak decrypted memory on unrecoverable errors

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.

Leak the decrypted memory when set_memory_decrypted() fails,
and don't need to print an error since set_memory_decrypted()
will call WARN_ONCE().

Fixes: f4738f56d1dc ("virt: tdx-guest: Add Quote generation support using TSM_REPORTS")
Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/all/20240619111801.25630-1-lirongqing%40baidu.com
---
 drivers/virt/coco/tdx-guest/tdx-guest.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/virt/coco/tdx-guest/tdx-guest.c b/drivers/virt/coco/tdx-guest/tdx-guest.c
index d7db6c8..224e7dd 100644
--- a/drivers/virt/coco/tdx-guest/tdx-guest.c
+++ b/drivers/virt/coco/tdx-guest/tdx-guest.c
@@ -124,10 +124,8 @@ static void *alloc_quote_buf(void)
 	if (!addr)
 		return NULL;
 
-	if (set_memory_decrypted((unsigned long)addr, count)) {
-		free_pages_exact(addr, len);
+	if (set_memory_decrypted((unsigned long)addr, count))
 		return NULL;
-	}
 
 	return addr;
 }