Commit 0559f630 authored by Ian Kent's avatar Ian Kent Committed by Greg Kroah-Hartman
Browse files

kernfs: fix missing kernfs_iattr_rwsem locking 



When the kernfs_iattr_rwsem was introduced a case was missed.

The update of the kernfs directory node child count was also protected
by the kernfs_rwsem and needs to be included in the change so that the
child count (and so the inode n_link attribute) does not change while
holding the rwsem for read.

Fixes: 9caf6961 ("kernfs: Introduce separate rwsem to protect inode attributes.")
Cc: stable <stable@kernel.org>
Signed-off-by: default avatarIan Kent <raven@themaw.net>
Reviewed-By: default avatarImran Khan <imran.f.khan@oracle.com>
Acked-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Cc: Anders Roxell <anders.roxell@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Eric Sandeen <sandeen@sandeen.net>
Link: https://lore.kernel.org/r/169128520941.68052.15749253469930138901.stgit@donald.themaw.net


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent bbaee49c

fs/kernfs/dir.c

+4 −0
Original line number Diff line number Diff line
@@ -383,9 +383,11 @@ static int kernfs_link_sibling(struct kernfs_node *kn) 
	rb_insert_color(&kn->rb, &kn->parent->dir.children);



	/* successfully added, account subdir number */

	down_write(&kernfs_root(kn)->kernfs_iattr_rwsem);

	if (kernfs_type(kn) == KERNFS_DIR)

		kn->parent->dir.subdirs++;

	kernfs_inc_rev(kn->parent);

	up_write(&kernfs_root(kn)->kernfs_iattr_rwsem);



	return 0;

}
@@ -408,9 +410,11 @@ static bool kernfs_unlink_sibling(struct kernfs_node *kn) 
	if (RB_EMPTY_NODE(&kn->rb))

		return false;



	down_write(&kernfs_root(kn)->kernfs_iattr_rwsem);

	if (kernfs_type(kn) == KERNFS_DIR)

		kn->parent->dir.subdirs--;

	kernfs_inc_rev(kn->parent);

	up_write(&kernfs_root(kn)->kernfs_iattr_rwsem);



	rb_erase(&kn->rb, &kn->parent->dir.children);

	RB_CLEAR_NODE(&kn->rb);