2022-07-12 15:35:50

by Liam R. Howlett

Subject: [PATCH] mm/mmap: Fix locking issues in vma_expand()

Hugh noted that the locking was mixed up in vma_expand(), revert to the
correct order.

Fixes: b2c87578e0ea (mm/mmap: use advanced maple tree API for mmap_region())
Suggested-by: Hugh Dickins <[email protected]>
Signed-off-by: Liam R. Howlett <[email protected]>
---
mm/mmap.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 9eb663cde5c7..9a07bc18e6aa 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -574,7 +574,8 @@ inline int vma_expand(struct ma_state *mas, struct vm_area_struct *vma,
if (next->anon_vma && !vma->anon_vma) {
int error;

- vma->anon_vma = next->anon_vma;
+ anon_vma = next->anon_vma;
+ vma->anon_vma = anon_vma;
error = anon_vma_clone(vma, next);
if (error)
return error;
@@ -592,16 +593,19 @@ inline int vma_expand(struct ma_state *mas, struct vm_area_struct *vma,

vma_adjust_trans_huge(vma, start, end, 0);

+ if (file) {
+ mapping = file->f_mapping;
+ root = &mapping->i_mmap;
+ uprobe_munmap(vma, vma->vm_start, vma->vm_end);
+ i_mmap_lock_write(mapping);
+ }
+
if (anon_vma) {
anon_vma_lock_write(anon_vma);
anon_vma_interval_tree_pre_update_vma(vma);
}

if (file) {
- mapping = file->f_mapping;
- root = &mapping->i_mmap;
- uprobe_munmap(vma, vma->vm_start, vma->vm_end);
- i_mmap_lock_write(mapping);
flush_dcache_mmap_lock(mapping);
vma_interval_tree_remove(vma, root);
}
@@ -622,16 +626,15 @@ inline int vma_expand(struct ma_state *mas, struct vm_area_struct *vma,
__remove_shared_vm_struct(next, file, mapping);
}

- if (file) {
- i_mmap_unlock_write(mapping);
- uprobe_mmap(vma);
- }
-
if (anon_vma) {
anon_vma_interval_tree_post_update_vma(vma);
anon_vma_unlock_write(anon_vma);
}

+ if (file) {
+ i_mmap_unlock_write(mapping);
+ uprobe_mmap(vma);
+ }

if (remove_next) {
if (file) {
--
2.35.1

2022-07-15 18:58:16

by Liam R. Howlett

Subject: Re: [PATCH] mm/mmap: Fix locking issues in vma_expand()

Andrew,

I think in my confusing post about ignoring the previous version of this
patch, you may have missed this completed solution?

Thanks,
Liam

* Liam R. Howlett <[email protected]> [220712 10:49]:
> Hugh noted that the locking was mixed up in vma_expand(), revert to the
> correct order.
>
> Fixes: b2c87578e0ea (mm/mmap: use advanced maple tree API for mmap_region())
> Suggested-by: Hugh Dickins <[email protected]>
> Signed-off-by: Liam R. Howlett <[email protected]>
> ---
> mm/mmap.c | 23 +++++++++++++----------
> 1 file changed, 13 insertions(+), 10 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 9eb663cde5c7..9a07bc18e6aa 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -574,7 +574,8 @@ inline int vma_expand(struct ma_state *mas, struct vm_area_struct *vma,
> if (next->anon_vma && !vma->anon_vma) {
> int error;
>
> - vma->anon_vma = next->anon_vma;
> + anon_vma = next->anon_vma;
> + vma->anon_vma = anon_vma;
> error = anon_vma_clone(vma, next);
> if (error)
> return error;
> @@ -592,16 +593,19 @@ inline int vma_expand(struct ma_state *mas, struct vm_area_struct *vma,
>
> vma_adjust_trans_huge(vma, start, end, 0);
>
> + if (file) {
> + mapping = file->f_mapping;
> + root = &mapping->i_mmap;
> + uprobe_munmap(vma, vma->vm_start, vma->vm_end);
> + i_mmap_lock_write(mapping);
> + }
> +
> if (anon_vma) {
> anon_vma_lock_write(anon_vma);
> anon_vma_interval_tree_pre_update_vma(vma);
> }
>
> if (file) {
> - mapping = file->f_mapping;
> - root = &mapping->i_mmap;
> - uprobe_munmap(vma, vma->vm_start, vma->vm_end);
> - i_mmap_lock_write(mapping);
> flush_dcache_mmap_lock(mapping);
> vma_interval_tree_remove(vma, root);
> }
> @@ -622,16 +626,15 @@ inline int vma_expand(struct ma_state *mas, struct vm_area_struct *vma,
> __remove_shared_vm_struct(next, file, mapping);
> }
>
> - if (file) {
> - i_mmap_unlock_write(mapping);
> - uprobe_mmap(vma);
> - }
> -
> if (anon_vma) {
> anon_vma_interval_tree_post_update_vma(vma);
> anon_vma_unlock_write(anon_vma);
> }
>
> + if (file) {
> + i_mmap_unlock_write(mapping);
> + uprobe_mmap(vma);
> + }
>
> if (remove_next) {
> if (file) {
> --
> 2.35.1

2022-07-15 23:55:39

by Andrew Morton

Subject: Re: [PATCH] mm/mmap: Fix locking issues in vma_expand()

On Fri, 15 Jul 2022 18:49:21 +0000 Liam Howlett <[email protected]> wrote:

>
> Andrew,
>
> I think in my confusing post about ignoring the previous version of this
> patch, you may have missed this completed solution?

Nope, this one is in -mm already.
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mmap-use-advanced-maple-tree-api-for-mmap_region-fix.patch