From: Jeff Xu jeffxu@google.com
This patch adds an architecture-independent function, arch_check_pkey_enforce_api(), that checks whether the calling thread has write access to the PKRU for a given range of memory. If the memory range is protected by PKEY_ENFORCE_API, then the thread must have write access to the PKRU in order to make changes to the memory mapping (such as mprotect/munmap).
This function is used by the kernel to enforce the PKEY_ENFORCE_API flag.
Signed-off-by: Jeff Xujeffxu@google.com --- arch/powerpc/include/asm/pkeys.h | 8 +++++ arch/x86/include/asm/pkeys.h | 50 ++++++++++++++++++++++++++++++++ include/linux/pkeys.h | 9 ++++++ 3 files changed, 67 insertions(+)
diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h index 943333ac0fee..24c481e5e95b 100644 --- a/arch/powerpc/include/asm/pkeys.h +++ b/arch/powerpc/include/asm/pkeys.h @@ -177,5 +177,13 @@ static inline bool arch_check_pkey_alloc_flags(unsigned long flags) return true; }
+static inline int arch_check_pkey_enforce_api(struct mm_struct *mm, + unsigned long start, + unsigned long end) +{ + /* Allow by default */ + return 0; +} + extern void pkey_mm_init(struct mm_struct *mm); #endif /*_ASM_POWERPC_KEYS_H */ diff --git a/arch/x86/include/asm/pkeys.h b/arch/x86/include/asm/pkeys.h index ecadf04a8251..8b94ffc4ca32 100644 --- a/arch/x86/include/asm/pkeys.h +++ b/arch/x86/include/asm/pkeys.h @@ -161,4 +161,54 @@ static inline bool arch_check_pkey_alloc_flags(unsigned long flags)
return true; } + +static inline int __arch_check_vma_pkey_for_write(struct vm_area_struct *vma) +{ + int pkey = vma_pkey(vma); + + if (mm_pkey_enforce_api(vma->vm_mm, pkey)) { + if (!__pkru_allows_write(read_pkru(), pkey)) + return -EACCES; + } + + return 0; +} + +/* + * arch_check_pkey_enforce_api is used by the kernel to enforce + * PKEY_ENFORCE_API flag. + * It checks whether the calling thread has write access to the PKRU + * for a given range of memory. If the memory range is protected by + * PKEY_ENFORCE_API, then the thread must have write access to the + * PKRU in order to make changes to the memory mapping, such as + * mprotect/munmap. + */ +static inline int arch_check_pkey_enforce_api(struct mm_struct *mm, + unsigned long start, + unsigned long end) +{ + int error; + struct vm_area_struct *vma; + + if (!arch_pkeys_enabled()) + return 0; + + while (true) { + vma = find_vma_intersection(mm, start, end); + if (!vma) + break; + + error = __arch_check_vma_pkey_for_write(vma); + if (error) + return error; + + if (vma->vm_end >= end) + break; + + start = vma->vm_end; + } + + return 0; +} + #endif /*_ASM_X86_PKEYS_H */ diff --git a/include/linux/pkeys.h b/include/linux/pkeys.h index 81a482c3e051..7b00689e1c24 100644 --- a/include/linux/pkeys.h +++ b/include/linux/pkeys.h @@ -53,6 +53,15 @@ static inline bool arch_check_pkey_alloc_flags(unsigned long flags) return false; return true; } + +static inline int arch_check_pkey_enforce_api(struct mm_struct *mm, + unsigned long start, + unsigned long end) +{ + // Allow by default. + return 0; +} + #endif /* ! CONFIG_ARCH_HAS_PKEYS */
#endif /* _LINUX_PKEYS_H */