crypto: ccp - Do not initialize SNP for ioctl(SNP_VLEK_LOAD)

Sashiko notes:

> if SEV initialization fails and KVM is actively running normal VMs, could a
> userspace process trigger this code path via /dev/sev ioctls (e.g.,
> SEV_PDH_GEN) and zero out MSR_VM_HSAVE_PA globally? Would the next VMRUN
> execution for an active VM trigger a general protection fault and crash the
> host?

The SEV firmware docs for SNP_VLEK_LOAD note:

> On SNP_SHUTDOWN, the VLEK is deleted.

That is, the initialization/shutdown wrapper here is pointless, because the
firmware immediately throws away the key anyway. Instead, refuse to do
anything if SNP has not been previously initialized.

This is an ABI break: before, this was a no-op and almost certainly a
mistake by userspace, and now it returns -ENODEV. ABI compatibility could be
maintained here by simply returning 0 in the check instead.

Fixes: ceac7fb89e8d ("crypto: ccp - Ensure implicit SEV/SNP init and shutdown in ioctls")
Reported-by: Sashiko
Assisted-by: Gemini:gemini-3.1-pro-preview
Link: https://sashiko.dev/#/patchset/20260324161301.1353976-1-tycho%40kernel.org
CC: <stable@vger.kernel.org>
Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index de472f0503cbefe3550e3285e3735be775c48152..9fb9267d7636e18a9acf5185d54b8bd5de22210a 100644 (file)
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -2484,9 +2484,8 @@ static int sev_ioctl_do_snp_vlek_load(struct sev_issue_cmd *argp, bool writable)
 {
        struct sev_device *sev = psp_master->sev_data;
        struct sev_user_data_snp_vlek_load input;
-       bool shutdown_required = false;
-       int ret, error;
        void *blob;
+       int ret;
 
        if (!argp->data)
                return -EINVAL;
@@ -2494,6 +2493,9 @@ static int sev_ioctl_do_snp_vlek_load(struct sev_issue_cmd *argp, bool writable)
        if (!writable)
                return -EPERM;
 
+       if (!sev->snp_initialized)
+               return -ENODEV;
+
        if (copy_from_user(&input, u64_to_user_ptr(argp->data), sizeof(input)))
                return -EFAULT;
 
@@ -2507,18 +2509,7 @@ static int sev_ioctl_do_snp_vlek_load(struct sev_issue_cmd *argp, bool writable)
 
        input.vlek_wrapped_address = __psp_pa(blob);
 
-       if (!sev->snp_initialized) {
-               ret = snp_move_to_init_state(argp, &shutdown_required);
-               if (ret)
-                       goto cleanup;
-       }
-
        ret = __sev_do_cmd_locked(SEV_CMD_SNP_VLEK_LOAD, &input, &argp->error);
-
-       if (shutdown_required)
-               __sev_snp_shutdown_locked(&error, false);
-
-cleanup:
        kfree(blob);
 
        return ret;