Sorry but there is something I dont understand. You ignored my point.Sorry, I missed it thinking that you are talking about another thing...
+void reset_files_struct(struct task_struct *tsk, struct files_struct *files)
+{
+ struct files_struct *old;
+
+ old = tsk->files;
+ task_lock(tsk);
+ tsk->files = files;
+ task_unlock(tsk);
+ put_files_struct(old);
+}
Its seems very strange to protect tsk->files = files with a task_lock()/task_unlock(). What is it supposed to guard against ???
If this patch corrects the 'bug', then a simpler fix would be to use a memory barrier between "tsk->files = files" and "put_files_struct(old);"
No need to perform 2 atomics ops on the task lock.
old = tsk->files;
tsk->files = files;
smp_mb();
put_files_struct(old);
That would be enough to guard against proc code (because this code only needs to read tsk->files of course)
The same remark can be said for __exit_files() from kernel/exit.c
If this task_lock()/task_unlock() patch is really needed, then a comment in the source would be very fair.