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From: KOSAKI Motohiro on 29 Jun 2010 20:40
> > This patch sanitizes task->comm to only contain printable characters
> > when it is set. Additionally, it redefines get_task_comm so that it is
> > more obvious when misused by callers (presently nothing was incorrectly
> > calling get_task_comm's unsafe use of strncpy).
>
> This is a regression for tools that correctly handle unmutilated data.
>
> > + /* sanitize non-printable characters */
> > + for (i = 0; buf[i] && i < (sizeof(tsk->comm) - 1); i++) {
> > + if (!isprint(buf[i]))
> > + tsk->comm[i] = '?';
>
> The kernel "isprint" isn't adequate for this. comm is set by the shell
> based on argv[0] usually which means that in normal situations it is a
> UTF-8 string.

Ah, I recall one use case. In past, some IBM folks talked about they
want to map Java thread name to prctl(PR_SET_NAME). In such case,
utf-8 name is very common.

So, I agree with you.

Thanks.



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From: Alan Cox on 30 Jun 2010 05:20
> What I do have interest in is fixing get_task_comm's use of buffers, which
> is theoretically problematic in some future where someone accidentally
> calls it with a buffer smaller than sizeof(task->comm).

Lots of things are theoretically problematic and kernel would take a week
to boot if we covered them all 8)

Having a
struct task_name {
char [propersize];
}

would produce the same code as far as I can tell and so typechecking
though - so as you say it can be done sanely.

Alan
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