From: Jeff Xu <[email protected]> can_modify_mm: checks sealing flags for given memory range.
can_modify_vma: checks sealing flags for given vma. Signed-off-by: Jeff Xu <[email protected]> --- include/linux/mm.h | 34 ++++++++++++++++++++++++++ mm/mseal.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 94 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index e790b91a0cd4..aafdb68950f8 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -257,6 +257,18 @@ extern struct rw_semaphore nommu_region_sem; extern unsigned int kobjsize(const void *objp); #endif +enum caller_origin { + ON_BEHALF_OF_KERNEL = 0, + ON_BEHALF_OF_USERSPACE, +}; + +enum mm_action { + MM_ACTION_MPROTECT, + MM_ACTION_MUNMAP, + MM_ACTION_MREMAP, + MM_ACTION_MMAP, +}; + /* * vm_seals in vm_area_struct, see mm_types.h. */ @@ -3302,6 +3314,28 @@ static inline void mm_populate(unsigned long addr, unsigned long len) static inline void mm_populate(unsigned long addr, unsigned long len) {} #endif +#ifdef CONFIG_MSEAL +extern bool can_modify_mm(struct mm_struct *mm, unsigned long start, + unsigned long end, enum mm_action action, + enum caller_origin called); + +extern bool can_modify_vma(struct vm_area_struct *vma, enum mm_action action, + enum caller_origin called); +#else +static inline bool can_modify_mm(struct mm_struct *mm, unsigned long start, + unsigned long end, enum mm_action action, + enum caller_origin called) +{ + return true; +} + +static inline bool can_modify_vma(struct vm_area_struct *vma, enum mm_action action, + enum caller_origin called) +{ + return true; +} +#endif + /* These take the mm semaphore themselves */ extern int __must_check vm_brk(unsigned long, unsigned long); extern int __must_check vm_brk_flags(unsigned long, unsigned long, unsigned long); diff --git a/mm/mseal.c b/mm/mseal.c index 615b6e06ab44..3285ef6b95a6 100644 --- a/mm/mseal.c +++ b/mm/mseal.c @@ -36,6 +36,66 @@ static bool can_do_mseal(unsigned int types, unsigned int flags) return true; } +/* + * check if a vma is sealed for modification. + * return true, if modification is allowed. + */ +bool can_modify_vma(struct vm_area_struct *vma, enum mm_action action, + enum caller_origin called) +{ + if (called == ON_BEHALF_OF_KERNEL) + return true; + + switch (action) { + case MM_ACTION_MPROTECT: + if (vma->vm_seals & VM_SEAL_MPROTECT) + return false; + break; + + case MM_ACTION_MUNMAP: + if (vma->vm_seals & VM_SEAL_MUNMAP) + return false; + break; + + case MM_ACTION_MREMAP: + if (vma->vm_seals & VM_SEAL_MREMAP) + return false; + break; + + case MM_ACTION_MMAP: + if (vma->vm_seals & VM_SEAL_MMAP) + return false; + break; + } + + return true; +} + +/* + * Check if the vmas of a memory range are allowed to be modified. + * the memory ranger can have a gap (unallocated memory). + * return true, if it is allowed. + */ +bool can_modify_mm(struct mm_struct *mm, unsigned long start, unsigned long end, + enum mm_action action, enum caller_origin called) +{ + struct vm_area_struct *vma; + + VMA_ITERATOR(vmi, mm, start); + + if (called == ON_BEHALF_OF_KERNEL) + return true; + + /* going through each vma to check */ + for_each_vma_range(vmi, vma, end) { + if (!can_modify_vma(vma, action, called)) + return false; + } + + /* Allow by default. */ + return true; +} + /* * Check if a seal type can be added to VMA. */ -- 2.42.0.609.gbb76f46606-goog
