Driver core: fix race in sysfs between sysfs_remove_file() and read()/write()

This patch prevents a race between IO and removing a file from sysfs.
It introduces a list of sysfs_buffers associated with a file at the inode.
Upon removal of a file the list is walked and the buffers marked orphaned.
IO to orphaned buffers fails with -ENODEV. The driver can safely free
associated data structures or be unloaded.

Signed-off-by: Oliver Neukum <oliver@neukum.name>
Acked-by: Maneesh Soni <maneesh@in.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 16 insertions, 0 deletions

diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index bd7cec295dab..39c623fdc277 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -33,6 +33,22 @@ struct sysfs_symlink {
 	struct kobject * target_kobj;
 };
 
+struct sysfs_buffer {
+	struct list_head		associates;
+	size_t				count;
+	loff_t				pos;
+	char				* page;
+	struct sysfs_ops		* ops;
+	struct semaphore		sem;
+	int				orphaned;
+	int				needs_read_fill;
+	int				event;
+};
+
+struct sysfs_buffer_collection {
+	struct list_head	associates;
+};
+
 static inline struct kobject * to_kobj(struct dentry * dentry)
 {
 	struct sysfs_dirent * sd = dentry->d_fsdata;