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    SubjectRe: [PATCH 2/3] printk: Add %ptc to safely print a task's comm
    On Tue, 2011-05-10 at 18:10 -0700, John Stultz wrote:
    > On Tue, 2011-05-10 at 17:51 -0700, Joe Perches wrote:
    > > Could misuse of %ptc (not using current) cause system lockup?
    > It very well could. Although I don't see other %p options tring to
    > handle invalid pointers. Any suggestions on how to best handle this?

    And just to clarify on this point, I'm responding to if a invalid
    pointer was provided, causing the dereference to go awry.

    If a valid non-current task was provided, the locking should be ok as we
    disable irqs while the write_seqlock is held in set_task_comm().

    The only places this could cause a problem was if you tried to printk
    with a %ptc while holding the task->comm_lock. However, the lock is only
    shortly held in task_comm_string, and get_task_comm and set_task_comm.
    So it is fairly easy to audit for correctness.

    If there is some other situation you had in mind, please let me know.


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