[v1] mm/mmap: Fix locking issues in vma_expand()

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

Posted by Liam Howlett 3 years, 9 months ago

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 <hughd@google.com>
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
---
 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

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

Posted by Liam Howlett 3 years, 9 months ago

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 <Liam.Howlett@oracle.com> [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 <hughd@google.com>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
> ---
>  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

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

Posted by Andrew Morton 3 years, 9 months ago

On Fri, 15 Jul 2022 18:49:21 +0000 Liam Howlett <liam.howlett@oracle.com> 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