2014-04-17 09:52:24

by Jianyu Zhan

Subject: [PATCH] kernfs: fix a subdir count leak

Currently kernfs_link_sibling() increates parent->dir.subdirs before
adding the node into parent's chidren rb tree.

Because it is possible that kernfs_link_sibling() couldn't find
a suitable slot and bail out, this leads to a mismatch between
elevated subdir count with actual children node numbers.

This patches fix this problem, by moving the subdir accouting
after the actual addtion happening.

Signed-off-by: Jianyu Zhan <[email protected]>
---
fs/kernfs/dir.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index 78f3403..ac127cd 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -232,9 +232,6 @@ static int kernfs_link_sibling(struct kernfs_node *kn)
struct rb_node **node = &kn->parent->dir.children.rb_node;
struct rb_node *parent = NULL;

- if (kernfs_type(kn) == KERNFS_DIR)
- kn->parent->dir.subdirs++;
-
while (*node) {
struct kernfs_node *pos;
int result;
@@ -249,9 +246,15 @@ static int kernfs_link_sibling(struct kernfs_node *kn)
else
return -EEXIST;
}
+
/* add new node and rebalance the tree */
rb_link_node(&kn->rb, parent, node);
rb_insert_color(&kn->rb, &kn->parent->dir.children);
+
+ /* successfully added, account subdir number */
+ if (kernfs_type(kn) == KERNFS_DIR)
+ kn->parent->dir.subdirs++;
+
return 0;
}

--
1.9.0.GIT

2014-04-17 13:19:24

by Tejun Heo

Subject: Re: [PATCH] kernfs: fix a subdir count leak

On Thu, Apr 17, 2014 at 05:52:10PM +0800, Jianyu Zhan wrote:
> Currently kernfs_link_sibling() increates parent->dir.subdirs before
> adding the node into parent's chidren rb tree.
>
> Because it is possible that kernfs_link_sibling() couldn't find
> a suitable slot and bail out, this leads to a mismatch between
> elevated subdir count with actual children node numbers.
>
> This patches fix this problem, by moving the subdir accouting
> after the actual addtion happening.
>
> Signed-off-by: Jianyu Zhan <[email protected]>

Acked-by: Tejun Heo <[email protected]>

Thanks.

--
tejun