[patch 004/166] mm: set vm_next and vm_prev to NULL in vm_area_dup()

Andrew Morton
2020-04-07T03:03:42Z

From: Li Xinhai <lixinhai.lxh@gmail.com>
Subject: mm: set vm_next and vm_prev to NULL in vm_area_dup()

Set ->vm_next and ->vm_prev to NULL to prevent potential misuse from the
new duplicated vma.

Currently, only in fork path there are misuse for handling anon_vma. No
other bugs been revealed with this patch applied.

Link: http://lkml.kernel.org/r/1581150928-3214-4-git-send-email-lixinhai.lxh@gmail.com
Signed-off-by: Li Xinhai <lixinhai.lxh@gmail.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

kernel/fork.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/fork.c~mm-set-vm_next-and-vm_prev-to-null-in-vm_area_dup
+++ a/kernel/fork.c
@@ -361,6 +361,7 @@ struct vm_area_struct *vm_area_dup(struc
if (new) {
*new = *orig;
INIT_LIST_HEAD(&new->anon_vma_chain);
+ new->vm_next = new->vm_prev = NULL;
}
return new;
}
@@ -562,7 +563,6 @@ static __latent_entropy int dup_mmap(str
} else if (anon_vma_fork(tmp, mpnt))
goto fail_nomem_anon_vma_fork;
tmp->vm_flags &= ~(VM_LOCKED | VM_LOCKONFAULT);
- tmp->vm_next = tmp->vm_prev = NULL;
file = tmp->vm_file;
if (file) {
struct inode *inode = file_inode(file);
_