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    SubjectRe: [PATCH -mm 1/1] ptrace: PTRACE_GETFDPIC: fix the unsafe usage of child->mm
    > You mean, pass it to arch_ptrace() ?
    > grep, grep, grep. I guess I understand you. We have more unsafe code
    > like this in arch/*/kernel/ptrace.c. Of course, it can be fixed without
    > doing get_task_mm() in sys_ptrace(), but perhaps it would be more clean
    > to do what you suggest.
    > Roland, what do you think?

    The mm pointer is only used by these uncommon ptrace operations that exist
    only in certain unusual arch's (and they're all ill-advised old arch ptrace
    ABI additions, at that). It doesn't seem wise to pay the overhead for
    get_task_mm()/mmput() on every ptrace call, 99.44% of which don't use it
    (and 100% on 90% of machines).

    If you were to make any change to the signature of arch_ptrace() it should
    be one big change to use a struct ptrace_params or suchlike, also passed
    down to ptrace_request(). Then any future needs to pass around more
    information won't require changing the code in all the arch code that
    doesn't look at the new parameter.


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