diff options
| author | Tycho Andersen (AMD) <tycho@kernel.org> | 2026-05-04 10:51:47 -0600 |
|---|---|---|
| committer | Herbert Xu <herbert@gondor.apana.org.au> | 2026-05-15 18:08:37 +0800 |
| commit | 08f0e65e784c4b20e6e620dd4f68d8636073a3d2 (patch) | |
| tree | f284c8202525b40de6fb6c5f28313541957a2681 /drivers/crypto | |
| parent | f91e9dbb5845d1e5abf1028e6df57dcf61583e1b (diff) | |
crypto: ccp - Do not initialize SNP for ioctl(SNP_CONFIG)
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?
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: <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>
Diffstat (limited to 'drivers/crypto')
| -rw-r--r-- | drivers/crypto/ccp/sev-dev.c | 33 |
1 files changed, 4 insertions, 29 deletions
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c index 9fb9267d7636..14df519ae7ee 100644 --- a/drivers/crypto/ccp/sev-dev.c +++ b/drivers/crypto/ccp/sev-dev.c @@ -1730,21 +1730,6 @@ 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; @@ -2454,8 +2439,6 @@ 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; @@ -2463,21 +2446,13 @@ 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) |