virt: sev-guest: Allocate request data dynamically

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")
Closes: https://github.com/AMDESE/AMDSEV/issues/265
Reported-by: andreas.stuehrk@yaxi.tech
Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20250307013700.437505-2-aik@amd.com

diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index 264b6523fe52feffb40dbd5a890655d8c80863a6..23ac177472beb896e1a584d73f9c7891736c78e0 100644 (file)
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -38,12 +38,6 @@ 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;
 };
 
 /*
@@ -71,7 +65,7 @@ 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 = {};
@@ -80,6 +74,10 @@ 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;
 
@@ -116,7 +114,7 @@ e_free:
 
 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 = {};
@@ -136,6 +134,10 @@ 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;
@@ -168,7 +170,7 @@ 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 = {};
@@ -178,6 +180,10 @@ 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;