vma_assert_write_locked() and vma_assert_attached() are useful for their own purposes, however VMA code absolutely does allow the modification of non-write locked VMAs if they are at that point detached (i.e. unreachable from anywhere).
It's therefore useful to be able to assert that a VMA is either detached (modification doesn't matter) or write locked (you're explicitly locked for modification). Therefore introduce vma_assert_can_modify() for this purpose. While we're here, make vma_is_attached() available generally - if !CONFIG_PER_VMA_LOCK, then there's no sense in which a VMA is detached (vma_mark_detached() is a noop), so have this default to true in this case. Also update VMA userland tests to reflect this change, correcting the previously open-coded vma_assert_[attached,detached]() there. Signed-off-by: Lorenzo Stoakes <[email protected]> --- include/linux/mmap_lock.h | 8 ++++++++ tools/testing/vma/include/dup.h | 15 +++++++++++++-- 2 files changed, 21 insertions(+), 2 deletions(-) diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h index 04b8f61ece5d..d513286d8160 100644 --- a/include/linux/mmap_lock.h +++ b/include/linux/mmap_lock.h @@ -506,6 +506,8 @@ static inline __must_check int vma_start_write_killable(struct vm_area_struct *vma) { return 0; } static inline void vma_assert_write_locked(struct vm_area_struct *vma) { mmap_assert_write_locked(vma->vm_mm); } +static inline bool vma_is_attached(struct vm_area_struct *vma) + { return true; } static inline void vma_assert_attached(struct vm_area_struct *vma) {} static inline void vma_assert_detached(struct vm_area_struct *vma) {} static inline void vma_mark_attached(struct vm_area_struct *vma) {} @@ -530,6 +532,12 @@ static inline void vma_assert_stabilised(struct vm_area_struct *vma) #endif /* CONFIG_PER_VMA_LOCK */ +static inline void vma_assert_can_modify(struct vm_area_struct *vma) +{ + if (vma_is_attached(vma)) + vma_assert_write_locked(vma); +} + static inline void mmap_write_lock(struct mm_struct *mm) { __mmap_lock_trace_start_locking(mm, true); diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h index 7ed165c8d9bc..e9ddc818f2c3 100644 --- a/tools/testing/vma/include/dup.h +++ b/tools/testing/vma/include/dup.h @@ -1163,6 +1163,11 @@ static inline struct vm_area_struct *vma_next(struct vma_iterator *vmi) return mas_find(&vmi->mas, ULONG_MAX); } +static inline bool vma_is_attached(struct vm_area_struct *vma) +{ + return refcount_read(&vma->vm_refcnt); +} + /* * WARNING: to avoid racing with vma_mark_attached()/vma_mark_detached(), these * assertions should be made either under mmap_write_lock or when the object @@ -1170,12 +1175,12 @@ static inline struct vm_area_struct *vma_next(struct vma_iterator *vmi) */ static inline void vma_assert_attached(struct vm_area_struct *vma) { - WARN_ON_ONCE(!refcount_read(&vma->vm_refcnt)); + WARN_ON_ONCE(!vma_is_attached(vma)); } static inline void vma_assert_detached(struct vm_area_struct *vma) { - WARN_ON_ONCE(refcount_read(&vma->vm_refcnt)); + WARN_ON_ONCE(vma_is_attached(vma)); } static inline void vma_assert_write_locked(struct vm_area_struct *); @@ -1564,3 +1569,9 @@ static inline pgoff_t linear_page_index(const struct vm_area_struct *vma, pgoff += vma_start_pgoff(vma); return pgoff; } + +static inline void vma_assert_can_modify(struct vm_area_struct *vma) +{ + if (vma_is_attached(vma)) + vma_assert_write_locked(vma); +} -- 2.55.0
