From: Shaohua Li <shli@xxxxxx> Add API to enable/disable writeprotect a vma range. Unlike mprotect, this doesn't split/merge vmas. Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Signed-off-by: Shaohua Li <shli@xxxxxx> Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> --- include/linux/userfaultfd_k.h | 2 ++ mm/userfaultfd.c | 52 +++++++++++++++++++++++++++++++++++ 2 files changed, 54 insertions(+) diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h index 38f748e7186e..e82f3156f4e9 100644 --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -37,6 +37,8 @@ extern ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long dst_start, unsigned long len, bool *mmap_changing); +extern int mwriteprotect_range(struct mm_struct *dst_mm, + unsigned long start, unsigned long len, bool enable_wp); /* mm helpers */ static inline bool is_mergeable_vm_userfaultfd_ctx(struct vm_area_struct *vma, diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index 458acda96f20..c38903f501c7 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -615,3 +615,55 @@ ssize_t mfill_zeropage(struct mm_struct *dst_mm, unsigned long start, { return __mcopy_atomic(dst_mm, start, 0, len, true, mmap_changing); } + +int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start, + unsigned long len, bool enable_wp) +{ + struct vm_area_struct *dst_vma; + pgprot_t newprot; + int err; + + /* + * Sanitize the command parameters: + */ + BUG_ON(start & ~PAGE_MASK); + BUG_ON(len & ~PAGE_MASK); + + /* Does the address range wrap, or is the span zero-sized? */ + BUG_ON(start + len <= start); + + down_read(&dst_mm->mmap_sem); + + /* + * Make sure the vma is not shared, that the dst range is + * both valid and fully within a single existing vma. + */ + err = -EINVAL; + dst_vma = find_vma(dst_mm, start); + if (!dst_vma || (dst_vma->vm_flags & VM_SHARED)) + goto out_unlock; + if (start < dst_vma->vm_start || + start + len > dst_vma->vm_end) + goto out_unlock; + + if (!dst_vma->vm_userfaultfd_ctx.ctx) + goto out_unlock; + if (!userfaultfd_wp(dst_vma)) + goto out_unlock; + + if (!vma_is_anonymous(dst_vma)) + goto out_unlock; + + if (enable_wp) + newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE)); + else + newprot = vm_get_page_prot(dst_vma->vm_flags); + + change_protection(dst_vma, start, start + len, newprot, + !enable_wp, 0); + + err = 0; +out_unlock: + up_read(&dst_mm->mmap_sem); + return err; +} -- 2.17.1