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SubjectRe: [PATCH 1/2] break out page allocation warning code
On Wed, 20 Apr 2011, KOSAKI Motohiro wrote:

> > That was true a while ago, but you now need to protect every thread's
> > ->comm with get_task_comm() or ensuring task_lock() is held to protect
> > against /proc/pid/comm which can change other thread's ->comm. That was
> > different before when prctl(PR_SET_NAME) would only operate on current, so
> > no lock was needed when reading current->comm.
>
> Right. /proc/pid/comm is evil. We have to fix it. otherwise we need change
> all of current->comm user. It's very lots!
>

Fixing it in this case would be removing it and only allowing it for
current via the usual prctl() :) The code was introduced in 4614a696bd1c
(procfs: allow threads to rename siblings via /proc/pid/tasks/tid/comm) in
December 2009 and seems to originally be meant for debugging. We simply
can't continue to let it modify any thread's ->comm unless we change the
over 300 current->comm deferences in the kernel.

I'd prefer that we remove /proc/pid/comm entirely or at least prevent
writing to it unless CONFIG_EXPERT.


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