enclave_map() is an SGX specific variant of file_mprotect() and mmap_file(), and is provided so that LSMs can apply W^X restrictions to enclaves. Due to the nature of SGX and its Enclave Page Cache (EPC), all enclave VMAs are backed by a single file, i.e. /dev/sgx/enclave, that must be MAP_SHARED. Furthermore, all enclaves need read, write and execute VMAs. As a result, applying W^X restrictions on /dev/sgx/enclave using existing LSM hooks is for all intents and purposes impossible, e.g. denying either W or X would deny access to any enclave. Note, extensive discussion yielded no sane alternative to some form of SGX specific LSM hook[1]. [1] https://lkml.kernel.org/r/CALCETrXf8mSK45h7sTK5Wf+pXLVn=Bjsc_RLpgO-h-qdzBRo5Q@xxxxxxxxxxxxxx Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> --- arch/x86/kernel/cpu/sgx/driver/main.c | 9 ++++++++- arch/x86/kernel/cpu/sgx/encl.c | 12 ++++++++++++ include/linux/lsm_hooks.h | 12 ++++++++++++ include/linux/security.h | 11 +++++++++++ security/security.c | 7 +++++++ 5 files changed, 50 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/sgx/driver/main.c b/arch/x86/kernel/cpu/sgx/driver/main.c index dabfe2a7245a..4379a2fb1f82 100644 --- a/arch/x86/kernel/cpu/sgx/driver/main.c +++ b/arch/x86/kernel/cpu/sgx/driver/main.c @@ -133,13 +133,20 @@ static unsigned long sgx_allowed_rwx(struct sgx_encl *encl, static int sgx_mmap(struct file *file, struct vm_area_struct *vma) { struct sgx_encl *encl = file->private_data; - unsigned long allowed_rwx; + unsigned long allowed_rwx, prot; int ret; allowed_rwx = sgx_allowed_rwx(encl, vma); if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC) & ~allowed_rwx) return -EACCES; + prot = _calc_vm_trans(vma->vm_flags, VM_READ, PROT_READ) | + _calc_vm_trans(vma->vm_flags, VM_WRITE, PROT_WRITE) | + _calc_vm_trans(vma->vm_flags, VM_EXEC, PROT_EXEC); + ret = security_enclave_map(prot); + if (ret) + return ret; + ret = sgx_encl_mm_add(encl, vma->vm_mm); if (ret) return ret; diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c index c6436bbd4a68..059d90dcaa27 100644 --- a/arch/x86/kernel/cpu/sgx/encl.c +++ b/arch/x86/kernel/cpu/sgx/encl.c @@ -2,6 +2,7 @@ // Copyright(c) 2016-18 Intel Corporation. #include <linux/mm.h> +#include <linux/security.h> #include <linux/shmem_fs.h> #include <linux/suspend.h> #include <linux/sched/mm.h> @@ -387,9 +388,20 @@ static int sgx_vma_access(struct vm_area_struct *vma, unsigned long addr, return ret < 0 ? ret : i; } +#ifdef CONFIG_SECURITY +static int sgx_vma_mprotect(struct vm_area_struct *vma, unsigned long start, + unsigned long end, unsigned long prot) +{ + return security_enclave_map(prot); +} +#endif + const struct vm_operations_struct sgx_vm_ops = { .fault = sgx_vma_fault, .access = sgx_vma_access, +#ifdef CONFIG_SECURITY + .may_mprotect = sgx_vma_mprotect, +#endif }; /** diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 47f58cfb6a19..7c1357105e61 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -1446,6 +1446,11 @@ * @bpf_prog_free_security: * Clean up the security information stored inside bpf prog. * + * Security hooks for Intel SGX enclaves. + * + * @enclave_map: + * @prot contains the protection that will be applied by the kernel. + * Return 0 if permission is granted. */ union security_list_options { int (*binder_set_context_mgr)(struct task_struct *mgr); @@ -1807,6 +1812,10 @@ union security_list_options { int (*bpf_prog_alloc_security)(struct bpf_prog_aux *aux); void (*bpf_prog_free_security)(struct bpf_prog_aux *aux); #endif /* CONFIG_BPF_SYSCALL */ + +#ifdef CONFIG_INTEL_SGX + int (*enclave_map)(unsigned long prot); +#endif /* CONFIG_INTEL_SGX */ }; struct security_hook_heads { @@ -2046,6 +2055,9 @@ struct security_hook_heads { struct hlist_head bpf_prog_alloc_security; struct hlist_head bpf_prog_free_security; #endif /* CONFIG_BPF_SYSCALL */ +#ifdef CONFIG_INTEL_SGX + struct hlist_head enclave_map; +#endif /* CONFIG_INTEL_SGX */ } __randomize_layout; /* diff --git a/include/linux/security.h b/include/linux/security.h index 659071c2e57c..6a1f54ba6794 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -1829,5 +1829,16 @@ static inline void security_bpf_prog_free(struct bpf_prog_aux *aux) #endif /* CONFIG_SECURITY */ #endif /* CONFIG_BPF_SYSCALL */ +#ifdef CONFIG_INTEL_SGX +#ifdef CONFIG_SECURITY +int security_enclave_map(unsigned long prot); +#else +static inline int security_enclave_map(unsigned long prot) +{ + return 0; +} +#endif /* CONFIG_SECURITY */ +#endif /* CONFIG_INTEL_SGX */ + #endif /* ! __LINUX_SECURITY_H */ diff --git a/security/security.c b/security/security.c index 613a5c00e602..03951e08bdfc 100644 --- a/security/security.c +++ b/security/security.c @@ -2359,3 +2359,10 @@ void security_bpf_prog_free(struct bpf_prog_aux *aux) call_void_hook(bpf_prog_free_security, aux); } #endif /* CONFIG_BPF_SYSCALL */ + +#ifdef CONFIG_INTEL_SGX +int security_enclave_map(unsigned long prot) +{ + return call_int_hook(enclave_map, 0, prot); +} +#endif /* CONFIG_INTEL_SGX */ -- 2.21.0
