kernel.git/arch/x86/kernel/cpu/sgx, branch linux-5.12.y

Merge tag 'x86_sgx_for_v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2021-02-21T03:13:18Z

Pull x86 SGX fixes from Borislav Petkov: "Random small fixes which missed the initial SGX submission. Also, some procedural clarifications" * tag 'x86_sgx_for_v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: MAINTAINERS: Add Dave Hansen as reviewer for INTEL SGX x86/sgx: Drop racy follow_pfn() check MAINTAINERS: Fix the tree location for INTEL SGX patches x86/sgx: Fix the return type of sgx_init()

x86/sgx: Maintain encl->refcount for each encl->mm_list entry

2021-02-08T18:11:30Z

This has been shown in tests: [ +0.000008] WARNING: CPU: 3 PID: 7620 at kernel/rcu/srcutree.c:374 cleanup_srcu_struct+0xed/0x100 This is essentially a use-after free, although SRCU notices it as an SRCU cleanup in an invalid context. == Background == SGX has a data structure (struct sgx_encl_mm) which keeps per-mm SGX metadata. This is separate from struct sgx_encl because, in theory, an enclave can be mapped from more than one mm. sgx_encl_mm includes a pointer back to the sgx_encl. This means that sgx_encl must have a longer lifetime than all of the sgx_encl_mm's that point to it. That's usually the case: sgx_encl_mm is freed only after the mmu_notifier is unregistered in sgx_release(). However, there's a race. If the process is exiting, sgx_mmu_notifier_release() can be called in parallel with sgx_release() instead of being called *by* it. The mmu_notifier path keeps encl_mm alive past when sgx_encl can be freed. This inverts the lifetime rules and means that sgx_mmu_notifier_release() can access a freed sgx_encl. == Fix == Increase encl->refcount when encl_mm->encl is established. Release this reference when encl_mm is freed. This ensures that encl outlives encl_mm. [ bp: Massage commit message. ] Fixes: 1728ab54b4be ("x86/sgx: Add a page reclaimer") Reported-by: Haitao Huang Signed-off-by: Jarkko Sakkinen Signed-off-by: Borislav Petkov Acked-by: Dave Hansen Link: https://lkml.kernel.org/r/20210207221401.29933-1-jarkko@kernel.org

x86/sgx: Drop racy follow_pfn() check

2021-02-05T09:45:11Z

PTE insertion is fundamentally racy, and this check doesn't do anything useful. Quoting Sean: "Yeah, it can be whacked. The original, never-upstreamed code asserted that the resolved PFN matched the PFN being installed by the fault handler as a sanity check on the SGX driver's EPC management. The WARN assertion got dropped for whatever reason, leaving that useless chunk." Jason stumbled over this as a new user of follow_pfn(), and I'm trying to get rid of unsafe callers of that function so it can be locked down further. This is independent prep work for the referenced patch series: https://lore.kernel.org/dri-devel/20201127164131.2244124-1-daniel.vetter@ffwll.ch/ Fixes: 947c6e11fa43 ("x86/sgx: Add ptrace() support for the SGX driver") Reported-by: Jason Gunthorpe Signed-off-by: Daniel Vetter Signed-off-by: Borislav Petkov Reviewed-by: Jarkko Sakkinen Link: https://lkml.kernel.org/r/20210204184519.2809313-1-daniel.vetter@ffwll.ch

x86/sgx: Fix the return type of sgx_init()

2021-01-21T13:04:06Z

device_initcall() expects a function of type initcall_t, which returns an integer. Change the signature of sgx_init() to match. Fixes: e7e0545299d8c ("x86/sgx: Initialize metadata for Enclave Page Cache (EPC) sections") Signed-off-by: Sami Tolvanen Signed-off-by: Borislav Petkov Reviewed-by: Darren Kenny Reviewed-by: Jarkko Sakkinen Link: https://lkml.kernel.org/r/20210113232311.277302-1-samitolvanen@google.com

x86/sgx: Return -EINVAL on a zero length buffer in sgx_ioc_enclave_add_pages()

2020-12-03T18:54:40Z

The sgx_enclave_add_pages.length field is documented as * @length: length of the data (multiple of the page size) Fail with -EINVAL, when the caller gives a zero length buffer of data to be added as pages to an enclave. Right now 'ret' is returned as uninitialized in that case. [ bp: Flesh out commit message. ] Fixes: c6d26d370767 ("x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES") Reported-by: Dan Carpenter Signed-off-by: Jarkko Sakkinen Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/linux-sgx/X8ehQssnslm194ld@mwanda/ Link: https://lkml.kernel.org/r/20201203183527.139317-1-jarkko@kernel.org

x86/sgx: Fix sgx_ioc_enclave_provision() kernel-doc comment

2020-11-24T09:46:01Z

Fix ./arch/x86/kernel/cpu/sgx/ioctl.c:666: warning: Function parameter or member \ 'encl' not described in 'sgx_ioc_enclave_provision' ./arch/x86/kernel/cpu/sgx/ioctl.c:666: warning: Excess function parameter \ 'enclave' description in 'sgx_ioc_enclave_provision' Reported-by: Stephen Rothwell Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20201123181922.0c009406@canb.auug.org.au

x86/sgx: Return -ERESTARTSYS in sgx_ioc_enclave_add_pages()

2020-11-19T09:51:24Z

Return -ERESTARTSYS instead of -EINTR in sgx_ioc_enclave_add_pages() when interrupted before any pages have been processed. At this point ioctl can be obviously safely restarted. Reported-by: Haitao Huang Signed-off-by: Jarkko Sakkinen Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20201118213932.63341-1-jarkko@kernel.org

x86/sgx: Clarify 'laundry_list' locking

2020-11-18T17:16:28Z

Short Version: The SGX section->laundry_list structure is effectively thread-local, but declared next to some shared structures. Its semantics are clear as mud. Fix that. No functional changes. Compile tested only. Long Version: The SGX hardware keeps per-page metadata. This can provide things like permissions, integrity and replay protection. It also prevents things like having an enclave page mapped multiple times or shared between enclaves. But, that presents a problem for kexec()'d kernels (or any other kernel that does not run immediately after a hardware reset). This is because the last kernel may have been rude and forgotten to reset pages, which would trigger the "shared page" sanity check. To fix this, the SGX code "launders" the pages by running the EREMOVE instruction on all pages at boot. This is slow and can take a long time, so it is performed off in the SGX-specific ksgxd instead of being synchronous at boot. The init code hands the list of pages to launder in a per-SGX-section list: ->laundry_list. The only code to touch this list is the init code and ksgxd. This means that no locking is necessary for ->laundry_list. However, a lock is required for section->page_list, which is accessed while creating enclaves and by ksgxd. This lock (section->lock) is acquired by ksgxd while also processing ->laundry_list. It is easy to confuse the purpose of the locking as being for ->laundry_list and ->page_list. Rename ->laundry_list to ->init_laundry_list to make it clear that this is not normally used at runtime. Also add some comments clarifying the locking, and reorganize 'sgx_epc_section' to put 'lock' near the things it protects. Note: init_laundry_list is 128 bytes of wasted space at runtime. It could theoretically be dynamically allocated and then freed after the laundering process. But it would take nearly 128 bytes of extra instructions to do that. Signed-off-by: Jarkko Sakkinen Signed-off-by: Dave Hansen Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20201116222531.4834-1-dave.hansen@intel.com

x86/sgx: Add ptrace() support for the SGX driver

2020-11-18T17:04:11Z

Enclave memory is normally inaccessible from outside the enclave. This makes enclaves hard to debug. However, enclaves can be put in a debug mode when they are being built. In that mode, enclave data *can* be read and/or written by using the ENCLS[EDBGRD] and ENCLS[EDBGWR] functions. This is obviously only for debugging and destroys all the protections present with normal enclaves. But, enclaves know their own debug status and can adjust their behavior appropriately. Add a vm_ops->access() implementation which can be used to read and write memory inside debug enclaves. This is typically used via ptrace() APIs. [ bp: Massage. ] Signed-off-by: Jarkko Sakkinen Signed-off-by: Borislav Petkov Tested-by: Jethro Beekman Link: https://lkml.kernel.org/r/20201112220135.165028-23-jarkko@kernel.org

x86/sgx: Add a page reclaimer

2020-11-18T17:04:11Z

Just like normal RAM, there is a limited amount of enclave memory available and overcommitting it is a very valuable tool to reduce resource use. Introduce a simple reclaim mechanism for enclave pages. In contrast to normal page reclaim, the kernel cannot directly access enclave memory. To get around this, the SGX architecture provides a set of functions to help. Among other things, these functions copy enclave memory to and from normal memory, encrypting it and protecting its integrity in the process. Implement a page reclaimer by using these functions. Picks victim pages in LRU fashion from all the enclaves running in the system. A new kernel thread (ksgxswapd) reclaims pages in the background based on watermarks, similar to normal kswapd. All enclave pages can be reclaimed, architecturally. But, there are some limits to this, such as the special SECS metadata page which must be reclaimed last. The page version array (used to mitigate replaying old reclaimed pages) is also architecturally reclaimable, but not yet implemented. The end result is that the vast majority of enclave pages are currently reclaimable. Co-developed-by: Sean Christopherson Signed-off-by: Sean Christopherson Signed-off-by: Jarkko Sakkinen Signed-off-by: Borislav Petkov Acked-by: Jethro Beekman Link: https://lkml.kernel.org/r/20201112220135.165028-22-jarkko@kernel.org