| Message ID | 20220520103904.1216-2-cathy.zhang@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Support microcode updates affecting SGX | expand |
On Fri, May 20, 2022 at 06:38:56PM +0800, Cathy Zhang wrote: > == Background == > > EUPDATESVN is a new SGX instruction which allows enclave attestation > to include information about updated microcode without a reboot. > > The SGX hardware maintains metadata for each enclave page to help > enforce its security guarantees. This includes things like a record > of the enclave to which the page belongs and the type of the page: > SGX metadata like "VA" or "SECS" pages, or regular enclave pages > like those that store user data. > > Before an EUPDATESVN operation can be successful, all SGX memory (aka. > EPC) must be marked as "unused" in the SGX hardware metadata (aka, > EPCM). The SGX microcode now maintains a reference count of pages > which are unused to aid in determining when all pages reach the > "unused" state. > > Both bare-metal and KVM guest EPC must be made unused. To increase > the chance of a successful EUPDATESVN, the kernel prevents existing > enclaves from creating new, valid pages and prevents new enclave > creation (creating an enclave involves initializing a "SECS" page). > > The entire EUPDATESVN process is very slow since it potentially > affects gigabytes of enclave memory. It can potentially take seconds > or minutes to complete. Userspace may encounter -EBUSY errors during > the update and is expected to retry. > > == Patch contents == > > Introduce mechanism to prevent new initializations of EPC pages. > > Use a flag to indicate when SGX EPC pages are "locked", which means > it's not allowed to allocate new EPC page for use. Check it in all > paths that can initialize an EPC page. Use SRCU to ensure that the > flag is visible across the system before proceeding with an update. > > Add checks to all sites that call SGX instructions that can transition > pages from unused to initialized to ensure that the SRCU lock is held. > > Signed-off-by: Cathy Zhang <cathy.zhang@intel.com> > > --- > Changes since v4: > - Add "goto err" for *if* branch and remove *else* branch for less > branching for common (success) case in sgx_ioc_enclave_create(). > (Jarkko Sakkinen) > > Changes since v3: > - Rename lable "out" as "err" in sgx_ioc_enclave_create, update error > branch accordingly. (Jarrko Sakkinen) > > Changes since v2: > - Move out the SGX2 related change to remove the dependency. > (Jarkko Sakkinen, Reinette Chatre). > --- > arch/x86/kernel/cpu/sgx/encls.h | 8 ++++++ > arch/x86/kernel/cpu/sgx/sgx.h | 3 +++ > arch/x86/kernel/cpu/sgx/encl.c | 18 +++++++++++++ > arch/x86/kernel/cpu/sgx/ioctl.c | 48 ++++++++++++++++++++++++++------- > arch/x86/kernel/cpu/sgx/main.c | 37 +++++++++++++++++++++++++ > arch/x86/kernel/cpu/sgx/virt.c | 20 ++++++++++++++ > 6 files changed, 125 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/kernel/cpu/sgx/encls.h b/arch/x86/kernel/cpu/sgx/encls.h > index fa04a73daf9c..60321c5f5718 100644 > --- a/arch/x86/kernel/cpu/sgx/encls.h > +++ b/arch/x86/kernel/cpu/sgx/encls.h > @@ -138,6 +138,8 @@ static inline bool encls_failed(int ret) > > static inline int __ecreate(struct sgx_pageinfo *pginfo, void *secs) > { > + lockdep_assert_held(&sgx_lock_epc_srcu); > + > return __encls_2(ECREATE, pginfo, secs); > } > > @@ -148,6 +150,8 @@ static inline int __eextend(void *secs, void *addr) > > static inline int __eadd(struct sgx_pageinfo *pginfo, void *addr) > { > + lockdep_assert_held(&sgx_lock_epc_srcu); > + > return __encls_2(EADD, pginfo, addr); > } > > @@ -179,6 +183,8 @@ static inline int __etrack(void *addr) > static inline int __eldu(struct sgx_pageinfo *pginfo, void *addr, > void *va) > { > + lockdep_assert_held(&sgx_lock_epc_srcu); > + > return __encls_ret_3(ELDU, pginfo, addr, va); > } > > @@ -191,6 +197,8 @@ static inline int __epa(void *addr) > { > unsigned long rbx = SGX_PAGE_TYPE_VA; > > + lockdep_assert_held(&sgx_lock_epc_srcu); > + > return __encls_2(EPA, rbx, addr); > } > > diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h > index b30cee4de903..d7a1490d90bb 100644 > --- a/arch/x86/kernel/cpu/sgx/sgx.h > +++ b/arch/x86/kernel/cpu/sgx/sgx.h > @@ -103,4 +103,7 @@ static inline int __init sgx_vepc_init(void) > > void sgx_update_lepubkeyhash(u64 *lepubkeyhash); > > +extern struct srcu_struct sgx_lock_epc_srcu; > +bool sgx_epc_is_locked(void); > + > #endif /* _X86_SGX_H */ > diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c > index 9e01548f4586..39f7f5dc09fd 100644 > --- a/arch/x86/kernel/cpu/sgx/encl.c > +++ b/arch/x86/kernel/cpu/sgx/encl.c > @@ -284,6 +284,7 @@ static vm_fault_t sgx_vma_fault(struct vm_fault *vmf) > unsigned long phys_addr; > struct sgx_encl *encl; > vm_fault_t ret; > + int srcu_idx; > > encl = vma->vm_private_data; > > @@ -295,11 +296,18 @@ static vm_fault_t sgx_vma_fault(struct vm_fault *vmf) > if (unlikely(!encl)) > return VM_FAULT_SIGBUS; > > + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); > + if (sgx_epc_is_locked()) { > + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); > + return VM_FAULT_SIGBUS; > + } > + > mutex_lock(&encl->lock); > > entry = sgx_encl_load_page(encl, addr, vma->vm_flags); > if (IS_ERR(entry)) { > mutex_unlock(&encl->lock); > + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); > > if (PTR_ERR(entry) == -EBUSY) > return VM_FAULT_NOPAGE; > @@ -312,12 +320,14 @@ static vm_fault_t sgx_vma_fault(struct vm_fault *vmf) > ret = vmf_insert_pfn(vma, addr, PFN_DOWN(phys_addr)); > if (ret != VM_FAULT_NOPAGE) { > mutex_unlock(&encl->lock); > + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); > > return VM_FAULT_SIGBUS; > } > > sgx_encl_test_and_clear_young(vma->vm_mm, entry); > mutex_unlock(&encl->lock); > + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); > > return VM_FAULT_NOPAGE; > } > @@ -465,6 +475,7 @@ static int sgx_vma_access(struct vm_area_struct *vma, unsigned long addr, > struct sgx_encl_page *entry = NULL; > char data[sizeof(unsigned long)]; > unsigned long align; > + int srcu_idx; > int offset; > int cnt; > int ret = 0; > @@ -481,6 +492,12 @@ static int sgx_vma_access(struct vm_area_struct *vma, unsigned long addr, > return -EFAULT; > > for (i = 0; i < len; i += cnt) { > + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); > + if (sgx_epc_is_locked()) { > + ret = -EBUSY; > + goto out; > + } > + > entry = sgx_encl_reserve_page(encl, (addr + i) & PAGE_MASK, > vma->vm_flags); > if (IS_ERR(entry)) { > @@ -508,6 +525,7 @@ static int sgx_vma_access(struct vm_area_struct *vma, unsigned long addr, > > out: > mutex_unlock(&encl->lock); > + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); > > if (ret) > break; > diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c > index b3c2e8d58142..d62720ed1728 100644 > --- a/arch/x86/kernel/cpu/sgx/ioctl.c > +++ b/arch/x86/kernel/cpu/sgx/ioctl.c > @@ -147,24 +147,43 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs) > static long sgx_ioc_enclave_create(struct sgx_encl *encl, void __user *arg) > { > struct sgx_enclave_create create_arg; > + int srcu_idx; > void *secs; > int ret; > > - if (test_bit(SGX_ENCL_CREATED, &encl->flags)) > - return -EINVAL; > + if (test_bit(SGX_ENCL_CREATED, &encl->flags)) { > + ret = -EINVAL; > + goto err; > + } > > - if (copy_from_user(&create_arg, arg, sizeof(create_arg))) > - return -EFAULT; > + if (copy_from_user(&create_arg, arg, sizeof(create_arg))) { > + ret = -EFAULT; > + goto err; > + } > > secs = kmalloc(PAGE_SIZE, GFP_KERNEL); > - if (!secs) > - return -ENOMEM; > + if (!secs) { > + ret = -ENOMEM; > + goto err; > + } > > - if (copy_from_user(secs, (void __user *)create_arg.src, PAGE_SIZE)) > + if (copy_from_user(secs, (void __user *)create_arg.src, PAGE_SIZE)) { > ret = -EFAULT; > - else > - ret = sgx_encl_create(encl, secs); > + goto err; > + } > > + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); > + if (sgx_epc_is_locked()) { > + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); > + ret = -EBUSY; > + goto err; > + } > + > + ret = sgx_encl_create(encl, secs); > + > + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); > + > +err: > kfree(secs); > return ret; > } > @@ -418,6 +437,7 @@ static long sgx_ioc_enclave_add_pages(struct sgx_encl *encl, void __user *arg) > struct sgx_enclave_add_pages add_arg; > struct sgx_secinfo secinfo; > unsigned long c; > + int srcu_idx; > int ret; > > if (!test_bit(SGX_ENCL_CREATED, &encl->flags) || > @@ -455,8 +475,18 @@ static long sgx_ioc_enclave_add_pages(struct sgx_encl *encl, void __user *arg) > if (need_resched()) > cond_resched(); > > + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); > + if (sgx_epc_is_locked()) { > + ret = -EBUSY; > + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); > + break; > + } > + > ret = sgx_encl_add_page(encl, add_arg.src + c, add_arg.offset + c, > &secinfo, add_arg.flags); > + > + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); > + > if (ret) > break; > } > diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c > index 08c00c325cc6..ec2775652a50 100644 > --- a/arch/x86/kernel/cpu/sgx/main.c > +++ b/arch/x86/kernel/cpu/sgx/main.c > @@ -23,6 +23,17 @@ static int sgx_nr_epc_sections; > static struct task_struct *ksgxd_tsk; > static DECLARE_WAIT_QUEUE_HEAD(ksgxd_waitq); > static DEFINE_XARRAY(sgx_epc_address_space); > +/* > + * The flag sgx_epc_locked prevents any new SGX flows that > + * may attempt to allocate a new EPC page. > + */ > +static bool __rcu sgx_epc_locked; > +/* > + * By synchronizing around sgx_epc_locked SRCU ensures that any executing > + * SGX flows have completed before proceeding with an SVN update. New SGX flows > + * will be prevented from starting during an SVN update. > + */ > +DEFINE_SRCU(sgx_lock_epc_srcu); > > /* > * These variables are part of the state of the reclaimer, and must be accessed > @@ -404,6 +415,8 @@ static bool sgx_should_reclaim(unsigned long watermark) > > static int ksgxd(void *p) > { > + int srcu_idx; > + > set_freezable(); > > /* > @@ -424,9 +437,15 @@ static int ksgxd(void *p) > kthread_should_stop() || > sgx_should_reclaim(SGX_NR_HIGH_PAGES)); > > + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); > + if (sgx_epc_is_locked()) > + goto maybe_resched; > + > if (sgx_should_reclaim(SGX_NR_HIGH_PAGES)) > sgx_reclaim_pages(); > > +maybe_resched: > + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); > cond_resched(); > } > > @@ -969,3 +988,21 @@ static int __init sgx_init(void) > } > > device_initcall(sgx_init); > + > +static void sgx_lock_epc(void) > +{ > + sgx_epc_locked = true; > + synchronize_srcu(&sgx_lock_epc_srcu); > +} > + > +static void sgx_unlock_epc(void) > +{ > + sgx_epc_locked = false; > + synchronize_srcu(&sgx_lock_epc_srcu); > +} > + > +bool sgx_epc_is_locked(void) > +{ > + lockdep_assert_held(&sgx_lock_epc_srcu); > + return sgx_epc_locked; > +} > diff --git a/arch/x86/kernel/cpu/sgx/virt.c b/arch/x86/kernel/cpu/sgx/virt.c > index 6a77a14eee38..e953816d7c8b 100644 > --- a/arch/x86/kernel/cpu/sgx/virt.c > +++ b/arch/x86/kernel/cpu/sgx/virt.c > @@ -75,10 +75,21 @@ static vm_fault_t sgx_vepc_fault(struct vm_fault *vmf) > { > struct vm_area_struct *vma = vmf->vma; > struct sgx_vepc *vepc = vma->vm_private_data; > + int srcu_idx; > int ret; > > mutex_lock(&vepc->lock); > + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); > + > + if (sgx_epc_is_locked()) { > + ret = -EBUSY; > + goto out_unlock; > + } > + > ret = __sgx_vepc_fault(vepc, vma, vmf->address); > + > +out_unlock: > + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); > mutex_unlock(&vepc->lock); > > if (!ret) > @@ -331,6 +342,7 @@ int __init sgx_vepc_init(void) > int sgx_virt_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs, > int *trapnr) > { > + int srcu_idx; > int ret; > > /* > @@ -347,6 +359,12 @@ int sgx_virt_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs, > if (WARN_ON_ONCE(!access_ok(secs, PAGE_SIZE))) > return -EINVAL; > > + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); > + if (sgx_epc_is_locked()) { > + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); > + return -EBUSY; > + } > + > __uaccess_begin(); > ret = __ecreate(pageinfo, (void *)secs); > __uaccess_end(); > @@ -356,6 +374,8 @@ int sgx_virt_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs, > return -EFAULT; > } > > + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); > + > /* ECREATE doesn't return an error code, it faults or succeeds. */ > WARN_ON_ONCE(ret); > return 0; > -- > 2.17.1 > Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> BR, Jarkko
diff --git a/arch/x86/kernel/cpu/sgx/encls.h b/arch/x86/kernel/cpu/sgx/encls.h index fa04a73daf9c..60321c5f5718 100644 --- a/arch/x86/kernel/cpu/sgx/encls.h +++ b/arch/x86/kernel/cpu/sgx/encls.h @@ -138,6 +138,8 @@ static inline bool encls_failed(int ret) static inline int __ecreate(struct sgx_pageinfo *pginfo, void *secs) { + lockdep_assert_held(&sgx_lock_epc_srcu); + return __encls_2(ECREATE, pginfo, secs); } @@ -148,6 +150,8 @@ static inline int __eextend(void *secs, void *addr) static inline int __eadd(struct sgx_pageinfo *pginfo, void *addr) { + lockdep_assert_held(&sgx_lock_epc_srcu); + return __encls_2(EADD, pginfo, addr); } @@ -179,6 +183,8 @@ static inline int __etrack(void *addr) static inline int __eldu(struct sgx_pageinfo *pginfo, void *addr, void *va) { + lockdep_assert_held(&sgx_lock_epc_srcu); + return __encls_ret_3(ELDU, pginfo, addr, va); } @@ -191,6 +197,8 @@ static inline int __epa(void *addr) { unsigned long rbx = SGX_PAGE_TYPE_VA; + lockdep_assert_held(&sgx_lock_epc_srcu); + return __encls_2(EPA, rbx, addr); } diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h index b30cee4de903..d7a1490d90bb 100644 --- a/arch/x86/kernel/cpu/sgx/sgx.h +++ b/arch/x86/kernel/cpu/sgx/sgx.h @@ -103,4 +103,7 @@ static inline int __init sgx_vepc_init(void) void sgx_update_lepubkeyhash(u64 *lepubkeyhash); +extern struct srcu_struct sgx_lock_epc_srcu; +bool sgx_epc_is_locked(void); + #endif /* _X86_SGX_H */ diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c index 9e01548f4586..39f7f5dc09fd 100644 --- a/arch/x86/kernel/cpu/sgx/encl.c +++ b/arch/x86/kernel/cpu/sgx/encl.c @@ -284,6 +284,7 @@ static vm_fault_t sgx_vma_fault(struct vm_fault *vmf) unsigned long phys_addr; struct sgx_encl *encl; vm_fault_t ret; + int srcu_idx; encl = vma->vm_private_data; @@ -295,11 +296,18 @@ static vm_fault_t sgx_vma_fault(struct vm_fault *vmf) if (unlikely(!encl)) return VM_FAULT_SIGBUS; + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); + if (sgx_epc_is_locked()) { + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); + return VM_FAULT_SIGBUS; + } + mutex_lock(&encl->lock); entry = sgx_encl_load_page(encl, addr, vma->vm_flags); if (IS_ERR(entry)) { mutex_unlock(&encl->lock); + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); if (PTR_ERR(entry) == -EBUSY) return VM_FAULT_NOPAGE; @@ -312,12 +320,14 @@ static vm_fault_t sgx_vma_fault(struct vm_fault *vmf) ret = vmf_insert_pfn(vma, addr, PFN_DOWN(phys_addr)); if (ret != VM_FAULT_NOPAGE) { mutex_unlock(&encl->lock); + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); return VM_FAULT_SIGBUS; } sgx_encl_test_and_clear_young(vma->vm_mm, entry); mutex_unlock(&encl->lock); + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); return VM_FAULT_NOPAGE; } @@ -465,6 +475,7 @@ static int sgx_vma_access(struct vm_area_struct *vma, unsigned long addr, struct sgx_encl_page *entry = NULL; char data[sizeof(unsigned long)]; unsigned long align; + int srcu_idx; int offset; int cnt; int ret = 0; @@ -481,6 +492,12 @@ static int sgx_vma_access(struct vm_area_struct *vma, unsigned long addr, return -EFAULT; for (i = 0; i < len; i += cnt) { + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); + if (sgx_epc_is_locked()) { + ret = -EBUSY; + goto out; + } + entry = sgx_encl_reserve_page(encl, (addr + i) & PAGE_MASK, vma->vm_flags); if (IS_ERR(entry)) { @@ -508,6 +525,7 @@ static int sgx_vma_access(struct vm_area_struct *vma, unsigned long addr, out: mutex_unlock(&encl->lock); + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); if (ret) break; diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c index b3c2e8d58142..d62720ed1728 100644 --- a/arch/x86/kernel/cpu/sgx/ioctl.c +++ b/arch/x86/kernel/cpu/sgx/ioctl.c @@ -147,24 +147,43 @@ static int sgx_encl_create(struct sgx_encl *encl, struct sgx_secs *secs) static long sgx_ioc_enclave_create(struct sgx_encl *encl, void __user *arg) { struct sgx_enclave_create create_arg; + int srcu_idx; void *secs; int ret; - if (test_bit(SGX_ENCL_CREATED, &encl->flags)) - return -EINVAL; + if (test_bit(SGX_ENCL_CREATED, &encl->flags)) { + ret = -EINVAL; + goto err; + } - if (copy_from_user(&create_arg, arg, sizeof(create_arg))) - return -EFAULT; + if (copy_from_user(&create_arg, arg, sizeof(create_arg))) { + ret = -EFAULT; + goto err; + } secs = kmalloc(PAGE_SIZE, GFP_KERNEL); - if (!secs) - return -ENOMEM; + if (!secs) { + ret = -ENOMEM; + goto err; + } - if (copy_from_user(secs, (void __user *)create_arg.src, PAGE_SIZE)) + if (copy_from_user(secs, (void __user *)create_arg.src, PAGE_SIZE)) { ret = -EFAULT; - else - ret = sgx_encl_create(encl, secs); + goto err; + } + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); + if (sgx_epc_is_locked()) { + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); + ret = -EBUSY; + goto err; + } + + ret = sgx_encl_create(encl, secs); + + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); + +err: kfree(secs); return ret; } @@ -418,6 +437,7 @@ static long sgx_ioc_enclave_add_pages(struct sgx_encl *encl, void __user *arg) struct sgx_enclave_add_pages add_arg; struct sgx_secinfo secinfo; unsigned long c; + int srcu_idx; int ret; if (!test_bit(SGX_ENCL_CREATED, &encl->flags) || @@ -455,8 +475,18 @@ static long sgx_ioc_enclave_add_pages(struct sgx_encl *encl, void __user *arg) if (need_resched()) cond_resched(); + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); + if (sgx_epc_is_locked()) { + ret = -EBUSY; + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); + break; + } + ret = sgx_encl_add_page(encl, add_arg.src + c, add_arg.offset + c, &secinfo, add_arg.flags); + + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); + if (ret) break; } diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c index 08c00c325cc6..ec2775652a50 100644 --- a/arch/x86/kernel/cpu/sgx/main.c +++ b/arch/x86/kernel/cpu/sgx/main.c @@ -23,6 +23,17 @@ static int sgx_nr_epc_sections; static struct task_struct *ksgxd_tsk; static DECLARE_WAIT_QUEUE_HEAD(ksgxd_waitq); static DEFINE_XARRAY(sgx_epc_address_space); +/* + * The flag sgx_epc_locked prevents any new SGX flows that + * may attempt to allocate a new EPC page. + */ +static bool __rcu sgx_epc_locked; +/* + * By synchronizing around sgx_epc_locked SRCU ensures that any executing + * SGX flows have completed before proceeding with an SVN update. New SGX flows + * will be prevented from starting during an SVN update. + */ +DEFINE_SRCU(sgx_lock_epc_srcu); /* * These variables are part of the state of the reclaimer, and must be accessed @@ -404,6 +415,8 @@ static bool sgx_should_reclaim(unsigned long watermark) static int ksgxd(void *p) { + int srcu_idx; + set_freezable(); /* @@ -424,9 +437,15 @@ static int ksgxd(void *p) kthread_should_stop() || sgx_should_reclaim(SGX_NR_HIGH_PAGES)); + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); + if (sgx_epc_is_locked()) + goto maybe_resched; + if (sgx_should_reclaim(SGX_NR_HIGH_PAGES)) sgx_reclaim_pages(); +maybe_resched: + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); cond_resched(); } @@ -969,3 +988,21 @@ static int __init sgx_init(void) } device_initcall(sgx_init); + +static void sgx_lock_epc(void) +{ + sgx_epc_locked = true; + synchronize_srcu(&sgx_lock_epc_srcu); +} + +static void sgx_unlock_epc(void) +{ + sgx_epc_locked = false; + synchronize_srcu(&sgx_lock_epc_srcu); +} + +bool sgx_epc_is_locked(void) +{ + lockdep_assert_held(&sgx_lock_epc_srcu); + return sgx_epc_locked; +} diff --git a/arch/x86/kernel/cpu/sgx/virt.c b/arch/x86/kernel/cpu/sgx/virt.c index 6a77a14eee38..e953816d7c8b 100644 --- a/arch/x86/kernel/cpu/sgx/virt.c +++ b/arch/x86/kernel/cpu/sgx/virt.c @@ -75,10 +75,21 @@ static vm_fault_t sgx_vepc_fault(struct vm_fault *vmf) { struct vm_area_struct *vma = vmf->vma; struct sgx_vepc *vepc = vma->vm_private_data; + int srcu_idx; int ret; mutex_lock(&vepc->lock); + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); + + if (sgx_epc_is_locked()) { + ret = -EBUSY; + goto out_unlock; + } + ret = __sgx_vepc_fault(vepc, vma, vmf->address); + +out_unlock: + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); mutex_unlock(&vepc->lock); if (!ret) @@ -331,6 +342,7 @@ int __init sgx_vepc_init(void) int sgx_virt_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs, int *trapnr) { + int srcu_idx; int ret; /* @@ -347,6 +359,12 @@ int sgx_virt_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs, if (WARN_ON_ONCE(!access_ok(secs, PAGE_SIZE))) return -EINVAL; + srcu_idx = srcu_read_lock(&sgx_lock_epc_srcu); + if (sgx_epc_is_locked()) { + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); + return -EBUSY; + } + __uaccess_begin(); ret = __ecreate(pageinfo, (void *)secs); __uaccess_end(); @@ -356,6 +374,8 @@ int sgx_virt_ecreate(struct sgx_pageinfo *pageinfo, void __user *secs, return -EFAULT; } + srcu_read_unlock(&sgx_lock_epc_srcu, srcu_idx); + /* ECREATE doesn't return an error code, it faults or succeeds. */ WARN_ON_ONCE(ret); return 0;
== Background == EUPDATESVN is a new SGX instruction which allows enclave attestation to include information about updated microcode without a reboot. The SGX hardware maintains metadata for each enclave page to help enforce its security guarantees. This includes things like a record of the enclave to which the page belongs and the type of the page: SGX metadata like "VA" or "SECS" pages, or regular enclave pages like those that store user data. Before an EUPDATESVN operation can be successful, all SGX memory (aka. EPC) must be marked as "unused" in the SGX hardware metadata (aka, EPCM). The SGX microcode now maintains a reference count of pages which are unused to aid in determining when all pages reach the "unused" state. Both bare-metal and KVM guest EPC must be made unused. To increase the chance of a successful EUPDATESVN, the kernel prevents existing enclaves from creating new, valid pages and prevents new enclave creation (creating an enclave involves initializing a "SECS" page). The entire EUPDATESVN process is very slow since it potentially affects gigabytes of enclave memory. It can potentially take seconds or minutes to complete. Userspace may encounter -EBUSY errors during the update and is expected to retry. == Patch contents == Introduce mechanism to prevent new initializations of EPC pages. Use a flag to indicate when SGX EPC pages are "locked", which means it's not allowed to allocate new EPC page for use. Check it in all paths that can initialize an EPC page. Use SRCU to ensure that the flag is visible across the system before proceeding with an update. Add checks to all sites that call SGX instructions that can transition pages from unused to initialized to ensure that the SRCU lock is held. Signed-off-by: Cathy Zhang <cathy.zhang@intel.com> --- Changes since v4: - Add "goto err" for *if* branch and remove *else* branch for less branching for common (success) case in sgx_ioc_enclave_create(). (Jarkko Sakkinen) Changes since v3: - Rename lable "out" as "err" in sgx_ioc_enclave_create, update error branch accordingly. (Jarrko Sakkinen) Changes since v2: - Move out the SGX2 related change to remove the dependency. (Jarkko Sakkinen, Reinette Chatre). --- arch/x86/kernel/cpu/sgx/encls.h | 8 ++++++ arch/x86/kernel/cpu/sgx/sgx.h | 3 +++ arch/x86/kernel/cpu/sgx/encl.c | 18 +++++++++++++ arch/x86/kernel/cpu/sgx/ioctl.c | 48 ++++++++++++++++++++++++++------- arch/x86/kernel/cpu/sgx/main.c | 37 +++++++++++++++++++++++++ arch/x86/kernel/cpu/sgx/virt.c | 20 ++++++++++++++ 6 files changed, 125 insertions(+), 9 deletions(-)