[PATCH] mm/rmap: synchronize lock and unlock target in anon_vma_clone

[PATCH] mm/rmap: synchronize lock and unlock target in anon_vma_clone

[Eric Kim]

Currently, in anon_vma_clone(), src vma's anon_vma is assigned to
active_anon_vma and is used when unlocking anon_vma after linking new
AVCs. However, the anon_vma is locked using src->anon_vma, instead of
active_anon_vma, making the lock and unlock target inconsistent.

Use active_anon_vma for both locking and unlocking.

Signed-off-by: Eric Kim <seohyun.kim@outlook.kr>
---
 mm/rmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/rmap.c b/mm/rmap.c
index 1c77d5dc06e9..f3fadfb69c7f 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -350,7 +350,7 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src,
 	 * Now link the anon_vma's back to the newly inserted AVCs.
 	 * Note that all anon_vma's share the same root.
 	 */
-	anon_vma_lock_write(src->anon_vma);
+	anon_vma_lock_write(active_anon_vma);
 	list_for_each_entry_reverse(avc, &dst->anon_vma_chain, same_vma) {
 		struct anon_vma *anon_vma = avc->anon_vma;
 
-- 
2.55.0

Re: [PATCH] mm/rmap: synchronize lock and unlock target in anon_vma_clone

[Lorenzo Stoakes (ARM)]

On Fri, Aug 14, 2026 at 03:30:51PM +0900, Eric Kim wrote:
> Currently, in anon_vma_clone(), src vma's anon_vma is assigned to
> active_anon_vma and is used when unlocking anon_vma after linking new
> AVCs. However, the anon_vma is locked using src->anon_vma, instead of
> active_anon_vma, making the lock and unlock target inconsistent.

IOW, I added active_anon_vma as an alias to src->anon_vma but didn't use it
consistently in the function :)

>
> Use active_anon_vma for both locking and unlocking.
>
> Signed-off-by: Eric Kim <seohyun.kim@outlook.kr>

LGTM, so:

Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>

> ---
>  mm/rmap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 1c77d5dc06e9..f3fadfb69c7f 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -350,7 +350,7 @@ int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src,
>  	 * Now link the anon_vma's back to the newly inserted AVCs.
>  	 * Note that all anon_vma's share the same root.
>  	 */
> -	anon_vma_lock_write(src->anon_vma);
> +	anon_vma_lock_write(active_anon_vma);
>  	list_for_each_entry_reverse(avc, &dst->anon_vma_chain, same_vma) {
>  		struct anon_vma *anon_vma = avc->anon_vma;
>
> --
> 2.55.0
>

--
Cheers, Lorenzo