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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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