[PATCH] kernfs: fix missing kernfs_idr_lock to remove an ID from the IDR

[PATCH] kernfs: fix missing kernfs_idr_lock to remove an ID from the IDR

[Muchun Song]

The root->ino_idr is supposed to be protected by kernfs_idr_lock, fix
it.

Fixes: 488dee96bb62 ("kernfs: allow creating kernfs objects with arbitrary uid/gid")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 fs/kernfs/dir.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 45b6919903e6..84a2cd196076 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -525,6 +525,13 @@ void kernfs_get(struct kernfs_node *kn)
 }
 EXPORT_SYMBOL_GPL(kernfs_get);
 
+static void kernfs_idr_remove(struct kernfs_root *root, struct kernfs_node *kn)
+{
+	spin_lock(&kernfs_idr_lock);
+	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
+	spin_unlock(&kernfs_idr_lock);
+}
+
 /**
  * kernfs_put - put a reference count on a kernfs_node
  * @kn: the target kernfs_node
@@ -559,9 +566,7 @@ void kernfs_put(struct kernfs_node *kn)
 		simple_xattrs_free(&kn->iattr->xattrs);
 		kmem_cache_free(kernfs_iattrs_cache, kn->iattr);
 	}
-	spin_lock(&kernfs_idr_lock);
-	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
-	spin_unlock(&kernfs_idr_lock);
+	kernfs_idr_remove(root, kn);
 	kmem_cache_free(kernfs_node_cache, kn);
 
 	kn = parent;
@@ -655,7 +660,7 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
 	return kn;
 
  err_out3:
-	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
+	kernfs_idr_remove(root, kn);
  err_out2:
 	kmem_cache_free(kernfs_node_cache, kn);
  err_out1:
-- 
2.11.0

Re: [PATCH] kernfs: fix missing kernfs_idr_lock to remove an ID from the IDR

[Tejun Heo]

On Tue, May 16, 2023 at 11:45:36AM +0800, Muchun Song wrote:
> @@ -655,7 +660,7 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
>  	return kn;
>  
>   err_out3:
> -	idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
> +	kernfs_idr_remove(root, kn);

Good catch but I'd just open code the locking here.

Thanks.

-- 
tejun

Re: [PATCH] kernfs: fix missing kernfs_idr_lock to remove an ID from the IDR

[Muchun Song]

> On May 23, 2023, at 03:08, Tejun Heo <tj@kernel.org> wrote:
> 
> On Tue, May 16, 2023 at 11:45:36AM +0800, Muchun Song wrote:
>> @@ -655,7 +660,7 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
>> return kn;
>> 
>>  err_out3:
>> - idr_remove(&root->ino_idr, (u32)kernfs_ino(kn));
>> + kernfs_idr_remove(root, kn);
> 
> Good catch but I'd just open code the locking here.

OK. I'll send v2.

Thanks.

> 
> Thanks.
> 
> -- 
> tejun