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;