[PATCH v3] fs/proc, core/debug: Don't expose absolute kernel addresses via wchan

[Ingo Molnar]

* Kees Cook <keescook@xxxxxxxxxxxx> wrote:

> > @@ -507,7 +505,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
> >         seq_put_decimal_ull(m, ' ', task->blocked.sig[0] & 0x7fffffffUL);
> >         seq_put_decimal_ull(m, ' ', sigign.sig[0] & 0x7fffffffUL);
> >         seq_put_decimal_ull(m, ' ', sigcatch.sig[0] & 0x7fffffffUL);
> > -       seq_put_decimal_ull(m, ' ', wchan);
> > +       seq_puts(m, " 0"); /* Used to be numeric wchan - replaced by /proc/PID/wchan */
> 
> Probably should also update Documentation/filesystems/proc.txt with
> something like:
> 
> --- a/Documentation/filesystems/proc.txt
> +++ b/Documentation/filesystems/proc.txt
> @@ -310,7 +310,7 @@ Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
>    blocked       bitmap of blocked signals
>    sigign        bitmap of ignored signals
>    sigcatch      bitmap of caught signals
> -  wchan         address where process went to sleep
> +  0             (place holder, was wchan, see /proc/PID/wchan instead)
>    0             (place holder)
>    0             (place holder)
>    exit_signal   signal to send to parent thread on exit

Indeed - I ended up clarifying both wchan explanations, see the changes below.

I also made the 'no symbols' output "0" (instead of an empty string), to better 
match the /proc/PID/stat behavior and previous output.

I'll push it out after a bit more testing and if nothing goes wrong I'll send this 
patch to Linus in the v4.4 merge window.

Thanks,

	Ingo

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