Messages in this thread | | | Date | Mon, 1 Feb 2016 19:04:43 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 4/4] sigaltstack: allow disabling and re-enabling sas within sighandler |
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On 02/01, Stas Sergeev wrote: > > 01.02.2016 20:09, Oleg Nesterov пишет: > >OK, I didn't notice you modified save_altstack_ex() to use ->sas_ss_flags instead > >of sas_ss_flags()... still doesn't look right, in this case restore_altstack() will > >not restore sas_ss_size/sas_ss_sp and they can be changed by signal handler. > How? > Trying to change them in a sighandler with sigaltstack() > will get EPERM.
Only if on_sig_stack() and this is not true if we change the stack.
> >Anyway, whatever I missed I agree with Andy, SS_FORCE looks simpler and better to me. > > But perhaps you missed the most important thing, that > it is not possible to change the altstack in sighandler - you'll > get EPERM, even with my patch.
See above.
> But with SS_FORCE this is > exactly not the case.
Yes, and SS_FORCE means "I know what I do", looks very simple.
> Also it would be interesting to know what do you think about > just removing the EPERM check instead of this all.
I won't argue, but to me it would be better to keep this EPERM if !force. Just because we should avoid the incompatible changes if possible.
Oleg.
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