Re: [PATCH v15 01/13] x86/sev: Carve out and export SNP guest messaging init routines

Nikunj A Dadhania
2024-12-10T06:38:44Z

On 12/9/2024 9:08 PM, Borislav Petkov wrote:
> On Mon, Dec 09, 2024 at 11:46:44AM +0530, Nikunj A. Dadhania wrote:
>> That leaves us with only one site: snp_init_crypto(), should I fold this
>> change in current patch ?
>
> Nah, a pre-patch pls.
>
> Along with an explanation summing up our discussion in the commit message.
> This patch is already doing enough.

From: Nikunj A Dadhania <nikunj@amd.com>
Date: Thu, 5 Dec 2024 12:00:56 +0530
Subject: [PATCH] virt: sev-guest: Replace GFP_KERNEL_ACCOUNT with GFP_KERNEL

Replace GFP_KERNEL_ACCOUNT with GFP_KERNEL in the sev-guest driver code.
GFP_KERNEL_ACCOUNT is typically used for accounting untrusted userspace
allocations. After auditing the sev-guest code, the following changes are
necessary:

* snp_init_crypto(): Use GFP_KERNEL as this is a trusted device probe
path.

Retain GFP_KERNEL_ACCOUNT in the following cases for robustness and
specific path requirements:

* alloc_shared_pages(): Although all allocations are limited, retain
GFP_KERNEL_ACCOUNT for future robustness.

* get_report() and get_ext_report(): These functions are on the unlocked
ioctl path and should continue using GFP_KERNEL_ACCOUNT.

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
---
drivers/virt/coco/sev-guest/sev-guest.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c
b/drivers/virt/coco/sev-guest/sev-guest.c
index 62328d0b2cb6..250ce92d816b 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -141,7 +141,7 @@ static struct aesgcm_ctx *snp_init_crypto(u8 *key, size_t
keylen)
{
struct aesgcm_ctx *ctx;

- ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
+ ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
return NULL;

--
2.34.1