The patch titled
Subject: kernel/fork: set VMA's mm/prev/next right after vm_area_dup in dup_mmap
has been added to the -mm tree. Its filename is
kernel-fork-set-vmas-mm-prev-next-right-after-vm_area_dup-in-dup_mmap.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kernel-fork-set-vmas-mm-prev-next-right-after-vm_area_dup-in-dup_mmap.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kernel-fork-set-vmas-mm-prev-next-right-after-vm_area_dup-in-dup_mmap.patch
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------------------------------------------------------
From: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Subject: kernel/fork: set VMA's mm/prev/next right after vm_area_dup in dup_mmap
Function vm_area_dup() makes exact copy of structure. It's better to stop
referencing parent structures because various helpers use these pointers.
For example if VM_WIPEONFORK is set then anon_vma_prepare() will try to
merge anon_vma with previous and next VMA. Poking parent VMAs and sharing
their anon_vma is safe for now but is not expected behavior.
Note: this will break commit 4e4a9eb92133 ("mm/rmap.c: reuse mergeable
anon_vma as parent when fork") without related fix because it contains
several flaws hidden by current initialization sequence in dup_mmap().
Link: http://lkml.kernel.org/r/157839239842.694.2288178566540902852.stgit@buzz
Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
Reviewed-by: Li Xinhai <lixinhai.lxh@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/fork.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
--- a/kernel/fork.c~kernel-fork-set-vmas-mm-prev-next-right-after-vm_area_dup-in-dup_mmap
+++ a/kernel/fork.c
@@ -544,10 +544,12 @@ static __latent_entropy int dup_mmap(str
tmp = vm_area_dup(mpnt);
if (!tmp)
goto fail_nomem;
+ tmp->vm_mm = mm;
+ tmp->vm_prev = prev;
+ tmp->vm_next = NULL;
retval = vma_dup_policy(mpnt, tmp);
if (retval)
goto fail_nomem_policy;
- tmp->vm_mm = mm;
retval = dup_userfaultfd(tmp, &uf);
if (retval)
goto fail_nomem_anon_vma_fork;
@@ -559,7 +561,6 @@ static __latent_entropy int dup_mmap(str
} else if (anon_vma_fork(tmp, mpnt, prev))
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);
@@ -592,7 +593,6 @@ static __latent_entropy int dup_mmap(str
*/
*pprev = tmp;
pprev = &tmp->vm_next;
- tmp->vm_prev = prev;
prev = tmp;
__vma_link_rb(mm, tmp, rb_link, rb_parent);
_
Patches currently in -mm which might be from khlebnikov@xxxxxxxxxxxxxx are
mm-rmap-fix-and-simplify-reusing-mergeable-anon_vma-as-parent-when-fork.patch
kernel-fork-set-vmas-mm-prev-next-right-after-vm_area_dup-in-dup_mmap.patch
