Commit fed95bab authored by Li Zefan's avatar Li Zefan Committed by Greg Kroah-Hartman
Browse files

sysfs: fix namespace refcnt leak 



As mount() and kill_sb() is not a one-to-one match, we shoudn't get
ns refcnt unconditionally in sysfs_mount(), and instead we should
get the refcnt only when kernfs_mount() allocated a new superblock.

v2:
- Changed the name of the new argument, suggested by Tejun.
- Made the argument optional, suggested by Tejun.

v3:
- Make the new argument as second-to-last arg, suggested by Tejun.

Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
 ---
 fs/kernfs/mount.c      | 8 +++++++-
 fs/sysfs/mount.c       | 5 +++--
 include/linux/kernfs.h | 9 +++++----
 3 files changed, 15 insertions(+), 7 deletions(-)
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 6d0abeca

fs/kernfs/mount.c

+7 −1
Original line number Diff line number Diff line
@@ -94,6 +94,7 @@ const void *kernfs_super_ns(struct super_block *sb) 
 * @fs_type: file_system_type of the fs being mounted

 * @flags: mount flags specified for the mount

 * @root: kernfs_root of the hierarchy being mounted

 * @new_sb_created: tell the caller if we allocated a new superblock

 * @ns: optional namespace tag of the mount

 *

 * This is to be called from each kernfs user's file_system_type->mount()
@@ -104,7 +105,8 @@ const void *kernfs_super_ns(struct super_block *sb) 
 * The return value can be passed to the vfs layer verbatim.

 */

struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,

			       struct kernfs_root *root, const void *ns)

			       struct kernfs_root *root, bool *new_sb_created,

			       const void *ns)

{

	struct super_block *sb;

	struct kernfs_super_info *info;
@@ -122,6 +124,10 @@ struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags, 
		kfree(info);

	if (IS_ERR(sb))

		return ERR_CAST(sb);



	if (new_sb_created)

		*new_sb_created = !sb->s_root;



	if (!sb->s_root) {

		error = kernfs_fill_super(sb);

		if (error) {

fs/sysfs/mount.c

+3 −2
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type, 
{

	struct dentry *root;

	void *ns;

	bool new_sb;



	if (!(flags & MS_KERNMOUNT)) {

		if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
@@ -37,8 +38,8 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type, 
	}



	ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);

	root = kernfs_mount_ns(fs_type, flags, sysfs_root, ns);

	if (IS_ERR(root))

	root = kernfs_mount_ns(fs_type, flags, sysfs_root, &new_sb, ns);

	if (IS_ERR(root) || !new_sb)

		kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);

	return root;

}

include/linux/kernfs.h

+5 −4
Original line number Diff line number Diff line
@@ -249,7 +249,8 @@ void kernfs_notify(struct kernfs_node *kn); 


const void *kernfs_super_ns(struct super_block *sb);

struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,

			       struct kernfs_root *root, const void *ns);

			       struct kernfs_root *root, bool *new_sb_created,

			       const void *ns);

void kernfs_kill_sb(struct super_block *sb);



void kernfs_init(void);
@@ -317,7 +318,7 @@ static inline const void *kernfs_super_ns(struct super_block *sb) 


static inline struct dentry *

kernfs_mount_ns(struct file_system_type *fs_type, int flags,

		struct kernfs_root *root, const void *ns)

		struct kernfs_root *root, bool *new_sb_created, const void *ns)

{ return ERR_PTR(-ENOSYS); }



static inline void kernfs_kill_sb(struct super_block *sb) { }
@@ -368,9 +369,9 @@ static inline int kernfs_remove_by_name(struct kernfs_node *parent, 


static inline struct dentry *

kernfs_mount(struct file_system_type *fs_type, int flags,

	     struct kernfs_root *root)

	     struct kernfs_root *root, bool *new_sb_created)

{

	return kernfs_mount_ns(fs_type, flags, root, NULL);

	return kernfs_mount_ns(fs_type, flags, root, new_sb_created, NULL);

}



#endif	/* __LINUX_KERNFS_H */

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