Re: [PATCH v2 4/4] crypto/ccp: Do not initialize SNP for ioctl(SNP_CONFIG)
From: Tom Lendacky <thomas.lendacky@amd.com>
Date: 2026-05-05 14:37:25
Also in:
lkml, stable
On 5/4/26 11:51, Tycho Andersen wrote:
From: "Tycho Andersen (AMD)" <tycho@kernel.org> Sashiko notes:quoted
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?Refuse to re-try initialization if SNP is not already initialized for SNP_CONFIG. This is technically an ABI break: before if SNP initialization failed it could be transparently retriggered by this ioctl, and if no VMs were running, everything worked fine. Hopefully this is enough of a corner case that nobody will notice, but someone does, there are a few options: * do something like symbol_get() for kvm and refuse to initialize if KVM is loaded * check each cpu's HSAVE_PA for non-zero data before re-initializing * once initialization has failed, continue to refuse to initialize until the ccp module is unloaded 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: <redacted> Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
quoted hunk ↗ jump to hunk
--- drivers/crypto/ccp/sev-dev.c | 33 ++++----------------------------- 1 file changed, 4 insertions(+), 29 deletions(-)diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c index ad6c2525a305..7c4dd57fabb9 100644 --- a/drivers/crypto/ccp/sev-dev.c +++ b/drivers/crypto/ccp/sev-dev.c@@ -1727,21 +1727,6 @@ static int sev_move_to_init_state(struct sev_issue_cmd *argp, bool *shutdown_req return 0; } -static int snp_move_to_init_state(struct sev_issue_cmd *argp, bool *shutdown_required) -{ - int error, rc; - - rc = __sev_snp_init_locked(&error, 0); - if (rc) { - argp->error = SEV_RET_INVALID_PLATFORM_STATE; - return rc; - } - - *shutdown_required = true; - - return 0; -} - static int sev_ioctl_do_reset(struct sev_issue_cmd *argp, bool writable) { int state, rc;@@ -2451,8 +2436,6 @@ static int sev_ioctl_do_snp_set_config(struct sev_issue_cmd *argp, bool writable { struct sev_device *sev = psp_master->sev_data; struct sev_user_data_snp_config config; - bool shutdown_required = false; - int ret, error; if (!argp->data) return -EINVAL;@@ -2460,21 +2443,13 @@ static int sev_ioctl_do_snp_set_config(struct sev_issue_cmd *argp, bool writable if (!writable) return -EPERM; + if (!sev->snp_initialized) + return -ENODEV; + if (copy_from_user(&config, (void __user *)argp->data, sizeof(config))) return -EFAULT; - if (!sev->snp_initialized) { - ret = snp_move_to_init_state(argp, &shutdown_required); - if (ret) - return ret; - } - - ret = __sev_do_cmd_locked(SEV_CMD_SNP_CONFIG, &config, &argp->error); - - if (shutdown_required) - __sev_snp_shutdown_locked(&error, false); - - return ret; + return __sev_do_cmd_locked(SEV_CMD_SNP_CONFIG, &config, &argp->error); } static int sev_ioctl_do_snp_vlek_load(struct sev_issue_cmd *argp, bool writable)