By the time VMA is freed it has to be detached with the exception of exit_mmap which is destroying the whole VMA tree. Enforce this requirement before freeing the VMA. exit_mmap in the only user calling __vm_area_free directly, therefore it won't trigger the new check. Change VMA initialization to mark new VMAs as detached and change that flag once the VMA is added into a tree. Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx> --- include/linux/mm.h | 4 ++-- kernel/fork.c | 2 ++ mm/internal.h | 1 + 3 files changed, 5 insertions(+), 2 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index 74e3033c9fc2..9a10fcdb134e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -247,7 +247,7 @@ void setup_initial_init_mm(void *start_code, void *end_code, struct vm_area_struct *vm_area_alloc(struct mm_struct *); struct vm_area_struct *vm_area_dup(struct vm_area_struct *); void vm_area_free(struct vm_area_struct *); -/* Use only if VMA has no other users */ +/* Use only if VMA has no other users and might still be attached to a tree */ void __vm_area_free(struct vm_area_struct *vma); #ifndef CONFIG_MMU @@ -751,7 +751,7 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm) vma->vm_mm = mm; vma->vm_ops = &dummy_vm_ops; INIT_LIST_HEAD(&vma->anon_vma_chain); - vma_mark_detached(vma, false); + vma->detached = true; vma_numab_state_init(vma); } diff --git a/kernel/fork.c b/kernel/fork.c index 41c964104b58..000fc429345c 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -540,6 +540,7 @@ static void vm_area_free_rcu_cb(struct rcu_head *head) /* The vma should not be locked while being destroyed. */ VM_BUG_ON_VMA(rwsem_is_locked(&vma->vm_lock->lock), vma); + WARN_ON_ONCE(!vma->detached); __vm_area_free(vma); } #endif @@ -549,6 +550,7 @@ void vm_area_free(struct vm_area_struct *vma) #ifdef CONFIG_PER_VMA_LOCK call_rcu(&vma->vm_rcu, vm_area_free_rcu_cb); #else + WARN_ON_ONCE(!vma->detached); __vm_area_free(vma); #endif } diff --git a/mm/internal.h b/mm/internal.h index 68410c6d97ac..728189e6c703 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1068,6 +1068,7 @@ static inline void vma_iter_store(struct vma_iterator *vmi, vmi->mas.index = vma->vm_start; vmi->mas.last = vma->vm_end - 1; mas_store_prealloc(&vmi->mas, vma); + vma_mark_detached(vma, false); } static inline int vma_iter_store_gfp(struct vma_iterator *vmi, -- 2.41.0.162.gfafddb0af9-goog
