diff options
Diffstat (limited to 'arch/x86/mm/fault.c')
| -rw-r--r-- | arch/x86/mm/fault.c | 29 |
1 files changed, 24 insertions, 5 deletions
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index e8711b2cafaf..ab778eac1952 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1112,8 +1112,22 @@ access_error(unsigned long error_code, struct vm_area_struct *vma) (error_code & X86_PF_INSTR), foreign)) return 1; + /* + * Shadow stack accesses (PF_SHSTK=1) are only permitted to + * shadow stack VMAs. All other accesses result in an error. + */ + if (error_code & X86_PF_SHSTK) { + if (unlikely(!(vma->vm_flags & VM_SHADOW_STACK))) + return 1; + if (unlikely(!(vma->vm_flags & VM_WRITE))) + return 1; + return 0; + } + if (error_code & X86_PF_WRITE) { /* write, present and write, not present: */ + if (unlikely(vma->vm_flags & VM_SHADOW_STACK)) + return 1; if (unlikely(!(vma->vm_flags & VM_WRITE))) return 1; return 0; @@ -1305,6 +1319,14 @@ void do_user_addr_fault(struct pt_regs *regs, perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); + /* + * Read-only permissions can not be expressed in shadow stack PTEs. + * Treat all shadow stack accesses as WRITE faults. This ensures + * that the MM will prepare everything (e.g., break COW) such that + * maybe_mkwrite() can create a proper shadow stack PTE. + */ + if (error_code & X86_PF_SHSTK) + flags |= FAULT_FLAG_WRITE; if (error_code & X86_PF_WRITE) flags |= FAULT_FLAG_WRITE; if (error_code & X86_PF_INSTR) @@ -1328,7 +1350,6 @@ void do_user_addr_fault(struct pt_regs *regs, } #endif -#ifdef CONFIG_PER_VMA_LOCK if (!(flags & FAULT_FLAG_USER)) goto lock_mmap; @@ -1341,7 +1362,8 @@ void do_user_addr_fault(struct pt_regs *regs, goto lock_mmap; } fault = handle_mm_fault(vma, address, flags | FAULT_FLAG_VMA_LOCK, regs); - vma_end_read(vma); + if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED))) + vma_end_read(vma); if (!(fault & VM_FAULT_RETRY)) { count_vm_vma_lock_event(VMA_LOCK_SUCCESS); @@ -1358,7 +1380,6 @@ void do_user_addr_fault(struct pt_regs *regs, return; } lock_mmap: -#endif /* CONFIG_PER_VMA_LOCK */ retry: vma = lock_mm_and_find_vma(mm, address, regs); @@ -1418,9 +1439,7 @@ retry: } mmap_read_unlock(mm); -#ifdef CONFIG_PER_VMA_LOCK done: -#endif if (likely(!(fault & VM_FAULT_ERROR))) return; |