| Message ID | 20230801220733.1987762-6-surenb@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | make vma locking more obvious | expand |
* Suren Baghdasaryan <surenb@google.com> [230801 18:07]: > While it's not strictly necessary to lock a newly created vma before > adding it into the vma tree (as long as no further changes are performed > to it), it seems like a good policy to lock it and prevent accidental > changes after it becomes visible to the page faults. Lock the vma before > adding it into the vma tree. > > Suggested-by: Jann Horn <jannh@google.com> > Signed-off-by: Suren Baghdasaryan <surenb@google.com> Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com> > --- > mm/mmap.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 3937479d0e07..850a39dee075 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -412,6 +412,8 @@ static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma) > if (vma_iter_prealloc(&vmi)) > return -ENOMEM; > > + vma_start_write(vma); > + > if (vma->vm_file) { > mapping = vma->vm_file->f_mapping; > i_mmap_lock_write(mapping); > @@ -477,7 +479,8 @@ static inline void vma_prepare(struct vma_prepare *vp) > vma_start_write(vp->vma); > if (vp->adj_next) > vma_start_write(vp->adj_next); > - /* vp->insert is always a newly created VMA, no need for locking */ > + if (vp->insert) > + vma_start_write(vp->insert); > if (vp->remove) > vma_start_write(vp->remove); > if (vp->remove2) > @@ -3098,6 +3101,7 @@ static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma, > vma->vm_pgoff = addr >> PAGE_SHIFT; > vm_flags_init(vma, flags); > vma->vm_page_prot = vm_get_page_prot(flags); > + vma_start_write(vma); > if (vma_iter_store_gfp(vmi, vma, GFP_KERNEL)) > goto mas_store_fail; > > @@ -3345,7 +3349,6 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, > get_file(new_vma->vm_file); > if (new_vma->vm_ops && new_vma->vm_ops->open) > new_vma->vm_ops->open(new_vma); > - vma_start_write(new_vma); > if (vma_link(mm, new_vma)) > goto out_vma_link; > *need_rmap_locks = false; > -- > 2.41.0.585.gd2178a4bd4-goog >
diff --git a/mm/mmap.c b/mm/mmap.c index 3937479d0e07..850a39dee075 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -412,6 +412,8 @@ static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma) if (vma_iter_prealloc(&vmi)) return -ENOMEM; + vma_start_write(vma); + if (vma->vm_file) { mapping = vma->vm_file->f_mapping; i_mmap_lock_write(mapping); @@ -477,7 +479,8 @@ static inline void vma_prepare(struct vma_prepare *vp) vma_start_write(vp->vma); if (vp->adj_next) vma_start_write(vp->adj_next); - /* vp->insert is always a newly created VMA, no need for locking */ + if (vp->insert) + vma_start_write(vp->insert); if (vp->remove) vma_start_write(vp->remove); if (vp->remove2) @@ -3098,6 +3101,7 @@ static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma, vma->vm_pgoff = addr >> PAGE_SHIFT; vm_flags_init(vma, flags); vma->vm_page_prot = vm_get_page_prot(flags); + vma_start_write(vma); if (vma_iter_store_gfp(vmi, vma, GFP_KERNEL)) goto mas_store_fail; @@ -3345,7 +3349,6 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap, get_file(new_vma->vm_file); if (new_vma->vm_ops && new_vma->vm_ops->open) new_vma->vm_ops->open(new_vma); - vma_start_write(new_vma); if (vma_link(mm, new_vma)) goto out_vma_link; *need_rmap_locks = false;
While it's not strictly necessary to lock a newly created vma before adding it into the vma tree (as long as no further changes are performed to it), it seems like a good policy to lock it and prevent accidental changes after it becomes visible to the page faults. Lock the vma before adding it into the vma tree. Suggested-by: Jann Horn <jannh@google.com> Signed-off-by: Suren Baghdasaryan <surenb@google.com> --- mm/mmap.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)