linux-kernel - [PATCH 1/2] virt: sev-guest: Allocate request data dynamically

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Message-ID: <20250307013700.437505-2-aik@amd.com>
Date: Fri, 7 Mar 2025 12:36:59 +1100
From: Alexey Kardashevskiy <aik@....com>
To: <x86@...nel.org>
CC: <linux-kernel@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>,
	"Ingo Molnar" <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen
	<dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>, Tom Lendacky
	<thomas.lendacky@....com>, Nikunj A Dadhania <nikunj@....com>, Ard Biesheuvel
	<ardb@...nel.org>, Pavan Kumar Paluri <papaluri@....com>, Ashish Kalra
	<ashish.kalra@....com>, Paolo Bonzini <pbonzini@...hat.com>, Michael Roth
	<michael.roth@....com>, Kevin Loughlin <kevinloughlin@...gle.com>,
	"Kuppuswamy Sathyanarayanan" <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	Brijesh Singh <brijesh.singh@....com>, Liam Merwick
	<liam.merwick@...cle.com>, "Alexey Kardashevskiy" <aik@....com>,
	<stable@...r.kernel.org>, <andreas.stuehrk@...i.tech>
Subject: [PATCH 1/2] virt: sev-guest: Allocate request data dynamically

From: Nikunj A Dadhania <nikunj@....com>

Commit ae596615d93d ("virt: sev-guest: Reduce the scope of SNP command
mutex") narrowed the command mutex scope to snp_send_guest_request.
However, GET_REPORT, GET_DERIVED_KEY, and GET_EXT_REPORT share the req
structure in snp_guest_dev. Without the mutex protection, concurrent
requests can overwrite each other's data. Fix it by dynamically allocating
the request structure.

Fixes: ae596615d93d ("virt: sev-guest: Reduce the scope of SNP command mutex")
Cc: stable@...r.kernel.org
Reported-by: andreas.stuehrk@...i.tech
Closes: https://github.com/AMDESE/AMDSEV/issues/265
Signed-off-by: Nikunj A Dadhania <nikunj@....com>
---
 drivers/virt/coco/sev-guest/sev-guest.c | 24 ++++++++++++--------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index ddec5677e247..4699fdc9ed44 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -39,12 +39,6 @@ struct snp_guest_dev {
 	struct miscdevice misc;
 
 	struct snp_msg_desc *msg_desc;
-
-	union {
-		struct snp_report_req report;
-		struct snp_derived_key_req derived_key;
-		struct snp_ext_report_req ext_report;
-	} req;
 };
 
 /*
@@ -72,7 +66,7 @@ struct snp_req_resp {
 
 static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
 {
-	struct snp_report_req *report_req = &snp_dev->req.report;
+	struct snp_report_req *report_req __free(kfree) = NULL;
 	struct snp_msg_desc *mdesc = snp_dev->msg_desc;
 	struct snp_report_resp *report_resp;
 	struct snp_guest_req req = {};
@@ -81,6 +75,10 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
 	if (!arg->req_data || !arg->resp_data)
 		return -EINVAL;
 
+	report_req = kzalloc(sizeof(*report_req), GFP_KERNEL_ACCOUNT);
+	if (!report_req)
+		return -ENOMEM;
+
 	if (copy_from_user(report_req, (void __user *)arg->req_data, sizeof(*report_req)))
 		return -EFAULT;
 
@@ -117,7 +115,7 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
 
 static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
 {
-	struct snp_derived_key_req *derived_key_req = &snp_dev->req.derived_key;
+	struct snp_derived_key_req *derived_key_req __free(kfree) = NULL;
 	struct snp_derived_key_resp derived_key_resp = {0};
 	struct snp_msg_desc *mdesc = snp_dev->msg_desc;
 	struct snp_guest_req req = {};
@@ -137,6 +135,10 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
 	if (sizeof(buf) < resp_len)
 		return -ENOMEM;
 
+	derived_key_req = kzalloc(sizeof(*derived_key_req), GFP_KERNEL_ACCOUNT);
+	if (!derived_key_req)
+		return -ENOMEM;
+
 	if (copy_from_user(derived_key_req, (void __user *)arg->req_data,
 			   sizeof(*derived_key_req)))
 		return -EFAULT;
@@ -169,7 +171,7 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
 			  struct snp_req_resp *io)
 
 {
-	struct snp_ext_report_req *report_req = &snp_dev->req.ext_report;
+	struct snp_ext_report_req *report_req __free(kfree) = NULL;
 	struct snp_msg_desc *mdesc = snp_dev->msg_desc;
 	struct snp_report_resp *report_resp;
 	struct snp_guest_req req = {};
@@ -179,6 +181,10 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
 	if (sockptr_is_null(io->req_data) || sockptr_is_null(io->resp_data))
 		return -EINVAL;
 
+	report_req = kzalloc(sizeof(*report_req), GFP_KERNEL_ACCOUNT);
+	if (!report_req)
+		return -ENOMEM;
+
 	if (copy_from_sockptr(report_req, io->req_data, sizeof(*report_req)))
 		return -EFAULT;
 
-- 
2.47.1