Race condition in fs/proc/array.c with task->comm

I searched for something about this, and I couldn't find anything.

I was having a problem with "top" crashing occasionally, so I looked, and top was getting nil characters in the process name in /proc/<pid>/stat. It turns out that there is a race condition when generating the output for task->comm. If the task "execs" during this time, it copies a new name into task->comm. When generating /proc/<pid>/stat, it uses sprintf to copy the string. However, if the data is changing in task->comm during this time, the results can be corrupted, including putting nil characters into the string.

This seems to be a problem in all version of the kernel I looked at (various 2.4 and 2.5 releases). I have only tested the problem in 2.4.20.

I can think it two main ways to fix this. You can:

* Make a local copy of task->comm. The results might still be wrong, but it will not contain nil characters.

* Use locks so the data is consistent.

I can fix this and supply a patch, but I'd like suggestions on which path to take. If suggesting a lock, should I create a new lock, or is there an existing lock I can use?

Thanks,

-Corey