linux/drivers/virt/coco, branch v6.8

virt: sev-guest: Convert to platform remove callback returning void

2024-01-02T18:07:18Z

The .remove() callback for a platform driver returns an int which makes many driver authors wrongly assume it's possible to do error handling by returning an error code. However the value returned is ignored (apart from emitting a warning) and this typically results in resource leaks. To improve here there is a quest to make the remove callback return void. In the first step of this quest all drivers are converted to .remove_new(), which already returns void. Eventually after all drivers are converted, .remove_new() will be renamed to .remove(). Trivially convert this driver from always returning zero in the remove callback to the void returning variant. Signed-off-by: Uwe Kleine-König Signed-off-by: Borislav Petkov (AMD) Acked-by: Tom Lendacky Link: https://lore.kernel.org/r/52826a50250304ab0af14c594009f7b901c2cd31.1703596577.git.u.kleine-koenig@pengutronix.de

virt: tdx-guest: Add Quote generation support using TSM_REPORTS

2023-10-20T01:12:00Z

In TDX guest, the attestation process is used to verify the TDX guest trustworthiness to other entities before provisioning secrets to the guest. The first step in the attestation process is TDREPORT generation, which involves getting the guest measurement data in the format of TDREPORT, which is further used to validate the authenticity of the TDX guest. TDREPORT by design is integrity-protected and can only be verified on the local machine. To support remote verification of the TDREPORT in a SGX-based attestation, the TDREPORT needs to be sent to the SGX Quoting Enclave (QE) to convert it to a remotely verifiable Quote. SGX QE by design can only run outside of the TDX guest (i.e. in a host process or in a normal VM) and guest can use communication channels like vsock or TCP/IP to send the TDREPORT to the QE. But for security concerns, the TDX guest may not support these communication channels. To handle such cases, TDX defines a GetQuote hypercall which can be used by the guest to request the host VMM to communicate with the SGX QE. More details about GetQuote hypercall can be found in TDX Guest-Host Communication Interface (GHCI) for Intel TDX 1.0, section titled "TDG.VP.VMCALL". Trusted Security Module (TSM) [1] exposes a common ABI for Confidential Computing Guest platforms to get the measurement data via ConfigFS. Extend the TSM framework and add support to allow an attestation agent to get the TDX Quote data (included usage example below). report=/sys/kernel/config/tsm/report/report0 mkdir $report dd if=/dev/urandom bs=64 count=1 > $report/inblob hexdump -C $report/outblob rmdir $report GetQuote TDVMCALL requires TD guest pass a 4K aligned shared buffer with TDREPORT data as input, which is further used by the VMM to copy the TD Quote result after successful Quote generation. To create the shared buffer, allocate a large enough memory and mark it shared using set_memory_decrypted() in tdx_guest_init(). This buffer will be re-used for GetQuote requests in the TDX TSM handler. Although this method reserves a fixed chunk of memory for GetQuote requests, such one time allocation can help avoid memory fragmentation related allocation failures later in the uptime of the guest. Since the Quote generation process is not time-critical or frequently used, the current version uses a polling model for Quote requests and it also does not support parallel GetQuote requests. Link: https://lore.kernel.org/lkml/169342399185.3934343.3035845348326944519.stgit@dwillia2-xfh.jf.intel.com/ [1] Signed-off-by: Kuppuswamy Sathyanarayanan Reviewed-by: Erdem Aktas Tested-by: Kuppuswamy Sathyanarayanan Tested-by: Peter Gonda Reviewed-by: Tom Lendacky Signed-off-by: Dan Williams

virt: sevguest: Add TSM_REPORTS support for SNP_GET_EXT_REPORT

2023-10-20T01:11:49Z

The sevguest driver was a first mover in the confidential computing space. As a first mover that afforded some leeway to build the driver without concern for common infrastructure. Now that sevguest is no longer a singleton [1] the common operation of building and transmitting attestation report blobs can / should be made common. In this model the so called "TSM-provider" implementations can share a common envelope ABI even if the contents of that envelope remain vendor-specific. When / if the industry agrees on an attestation record format, that definition can also fit in the same ABI. In the meantime the kernel's maintenance burden is reduced and collaboration on the commons is increased. Convert sevguest to use CONFIG_TSM_REPORTS to retrieve the data that the SNP_GET_EXT_REPORT ioctl produces. An example flow follows for retrieving the report blob via the TSM interface utility, assuming no nonce and VMPL==2: report=/sys/kernel/config/tsm/report/report0 mkdir $report echo 2 > $report/privlevel dd if=/dev/urandom bs=64 count=1 > $report/inblob hexdump -C $report/outblob # SNP report hexdump -C $report/auxblob # cert_table rmdir $report Given that the platform implementation is free to return empty certificate data if none is available it lets configfs-tsm be simplified as it only needs to worry about wrapping SNP_GET_EXT_REPORT, and leave SNP_GET_REPORT alone. The old ioctls can be lazily deprecated, the main motivation of this effort is to stop the proliferation of new ioctls, and to increase cross-vendor collaboration. Link: http://lore.kernel.org/r/64961c3baf8ce_142af829436@dwillia2-xfh.jf.intel.com.notmuch [1] Cc: Borislav Petkov Cc: Tom Lendacky Cc: Dionna Glaze Cc: Jeremi Piotrowski Tested-by: Kuppuswamy Sathyanarayanan Tested-by: Alexey Kardashevskiy Reviewed-by: Tom Lendacky Signed-off-by: Dan Williams

virt: sevguest: Prep for kernel internal get_ext_report()

2023-10-20T01:11:38Z

In preparation for using the configs-tsm facility to convey attestation blobs to userspace, switch to using the 'sockptr' api for copying payloads to provided buffers where 'sockptr' handles user vs kernel buffers. While configfs-tsm is meant to replace existing confidential computing ioctl() implementations for attestation report retrieval the old ioctl() path needs to stick around for a deprecation period. No behavior change intended. Cc: Borislav Petkov Cc: Tom Lendacky Cc: Dionna Glaze Reviewed-by: Kuppuswamy Sathyanarayanan Tested-by: Kuppuswamy Sathyanarayanan Reviewed-by: Tom Lendacky Signed-off-by: Dan Williams

configfs-tsm: Introduce a shared ABI for attestation reports

2023-10-20T01:11:38Z

One of the common operations of a TSM (Trusted Security Module) is to provide a way for a TVM (confidential computing guest execution environment) to take a measurement of its launch state, sign it and submit it to a verifying party. Upon successful attestation that verifies the integrity of the TVM additional secrets may be deployed. The concept is common across TSMs, but the implementations are unfortunately vendor specific. While the industry grapples with a common definition of this attestation format [1], Linux need not make this problem worse by defining a new ABI per TSM that wants to perform a similar operation. The current momentum has been to invent new ioctl-ABI per TSM per function which at best is an abdication of the kernel's responsibility to make common infrastructure concepts share common ABI. The proposal, targeted to conceptually work with TDX, SEV-SNP, COVE if not more, is to define a configfs interface to retrieve the TSM-specific blob. report=/sys/kernel/config/tsm/report/report0 mkdir $report dd if=binary_userdata_plus_nonce > $report/inblob hexdump $report/outblob This approach later allows for the standardization of the attestation blob format without needing to invent a new ABI. Once standardization happens the standard format can be emitted by $report/outblob and indicated by $report/provider, or a new attribute like "$report/tcg_coco_report" can emit the standard format alongside the vendor format. Review of previous iterations of this interface identified that there is a need to scale report generation for multiple container environments [2]. Configfs enables a model where each container can bind mount one or more report generation item instances. Still, within a container only a single thread can be manipulating a given configuration instance at a time. A 'generation' count is provided to detect conflicts between multiple threads racing to configure a report instance. The SEV-SNP concepts of "extended reports" and "privilege levels" are optionally enabled by selecting 'tsm_report_ext_type' at register_tsm() time. The expectation is that those concepts are generic enough that they may be adopted by other TSM implementations. In other words, configfs-tsm aims to address a superset of TSM specific functionality with a common ABI where attributes may appear, or not appear, based on the set of concepts the implementation supports. Link: http://lore.kernel.org/r/64961c3baf8ce_142af829436@dwillia2-xfh.jf.intel.com.notmuch [1] Link: http://lore.kernel.org/r/57f3a05e-8fcd-4656-beea-56bb8365ae64@linux.microsoft.com [2] Cc: Kuppuswamy Sathyanarayanan Cc: Dionna Amalie Glaze Cc: James Bottomley Cc: Peter Gonda Cc: Greg Kroah-Hartman Cc: Samuel Ortiz Acked-by: Greg Kroah-Hartman Acked-by: Thomas Gleixner Reviewed-by: Kuppuswamy Sathyanarayanan Tested-by: Kuppuswamy Sathyanarayanan Reviewed-by: Tom Lendacky Signed-off-by: Dan Williams

virt: coco: Add a coco/Makefile and coco/Kconfig

2023-10-20T01:11:38Z

In preparation for adding another coco build target, relieve drivers/virt/Makefile of the responsibility to track new compilation unit additions to drivers/virt/coco/, and do the same for drivers/virt/Kconfig. Reviewed-by: Kuppuswamy Sathyanarayanan Tested-by: Kuppuswamy Sathyanarayanan Reviewed-by: Tom Lendacky Signed-off-by: Dan Williams

virt: sevguest: Fix passing a stack buffer as a scatterlist target

2023-10-11T03:03:53Z

CONFIG_DEBUG_SG highlights that get_{report,ext_report,derived_key)()} are passing stack buffers as the @req_buf argument to handle_guest_request(), generating a Call Trace of the following form: WARNING: CPU: 0 PID: 1175 at include/linux/scatterlist.h:187 enc_dec_message+0x518/0x5b0 [sev_guest] [..] Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023 RIP: 0010:enc_dec_message+0x518/0x5b0 [sev_guest] Call Trace: [..] handle_guest_request+0x135/0x520 [sev_guest] get_ext_report+0x1ec/0x3e0 [sev_guest] snp_guest_ioctl+0x157/0x200 [sev_guest] Note that the above Call Trace was with the DEBUG_SG BUG_ON()s converted to WARN_ON()s. This is benign as long as there are no hardware crypto accelerators loaded for the aead cipher, and no subsequent dma_map_sg() is performed on the scatterlist. However, sev-guest can not assume the presence of an aead accelerator nor can it assume that CONFIG_DEBUG_SG is disabled. Resolve this bug by allocating virt_addr_valid() memory, similar to the other buffers am @snp_dev instance carries, to marshal requests from user buffers to kernel buffers. Reported-by: Peter Gonda Closes: http://lore.kernel.org/r/CAMkAt6r2VPPMZ__SQfJse8qWsUyYW3AgYbOUVM0S_Vtk=KvkxQ@mail.gmail.com Fixes: fce96cf04430 ("virt: Add SEV-SNP guest driver") Cc: Borislav Petkov Cc: Tom Lendacky Cc: Dionna Glaze Cc: Jeremi Piotrowski Tested-by: Kuppuswamy Sathyanarayanan Reviewed-by: Tom Lendacky Signed-off-by: Dan Williams

virt: sevguest: Add CONFIG_CRYPTO dependency

2023-06-09T13:53:07Z

This driver fails to link when CRYPTO is disabled, or in a loadable module: WARNING: unmet direct dependencies detected for CRYPTO_GCM WARNING: unmet direct dependencies detected for CRYPTO_AEAD2 Depends on [m]: CRYPTO [=m] Selected by [y]: - SEV_GUEST [=y] && VIRT_DRIVERS [=y] && AMD_MEM_ENCRYPT [=y] x86_64-linux-ld: crypto/aead.o: in function `crypto_register_aeads': Fixes: fce96cf04430 ("virt: Add SEV-SNP guest driver") Signed-off-by: Arnd Bergmann Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20230117171416.2715125-1-arnd@kernel.org

x86/sev: Change snp_guest_issue_request()'s fw_err argument

2023-03-21T14:43:19Z

The GHCB specification declares that the firmware error value for a guest request will be stored in the lower 32 bits of EXIT_INFO_2. The upper 32 bits are for the VMM's own error code. The fw_err argument to snp_guest_issue_request() is thus a misnomer, and callers will need access to all 64 bits. The type of unsigned long also causes problems, since sw_exit_info2 is u64 (unsigned long long) vs the argument's unsigned long*. Change this type for issuing the guest request. Pass the ioctl command struct's error field directly instead of in a local variable, since an incomplete guest request may not set the error code, and uninitialized stack memory would be written back to user space. The firmware might not even be called, so bookend the call with the no firmware call error and clear the error. Since the "fw_err" field is really exitinfo2 split into the upper bits' vmm error code and lower bits' firmware error code, convert the 64 bit value to a union. [ bp: - Massage commit message - adjust code - Fix a build issue as Reported-by: kernel test robot Link: https://lore.kernel.org/oe-kbuild-all/202303070609.vX6wp2Af-lkp@intel.com - print exitinfo2 in hex Tom: - Correct -EIO exit case. ] Signed-off-by: Dionna Glaze Signed-off-by: Tom Lendacky Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20230214164638.1189804-5-dionnaglaze@google.com Link: https://lore.kernel.org/r/20230307192449.24732-12-bp@alien8.de

virt/coco/sev-guest: Double-buffer messages

2023-03-21T12:20:04Z

The encryption algorithms read and write directly to shared unencrypted memory, which may leak information as well as permit the host to tamper with the message integrity. Instead, copy whole messages in or out as needed before doing any computation on them. Fixes: d5af44dde546 ("x86/sev: Provide support for SNP guest request NAEs") Signed-off-by: Dionna Glaze Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20230214164638.1189804-3-dionnaglaze@google.com