Messages in this thread | | | Date | Mon, 11 Mar 2013 20:28:05 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH] signal: always clear sa_restorer on execve |
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On 03/11, Kees Cook wrote: > > When the new signal handlers are set up for a fork, the location of > sa_restorer is not cleared, leaking a parent process's address space > location to children. This allows for a potential bypass of the parent's > ASLR by examining the sa_restorer value returned when calling sigaction().
I don't understand.
fork() should not change restorer/etc, and the child has the same address space anyway. There is no any leak and the patch can't make any difference in this case because flush_signal_handlers() is not called by fork().
> @@ -485,6 +485,9 @@ flush_signal_handlers(struct task_struct *t, int force_default) > if (force_default || ka->sa.sa_handler != SIG_IGN) > ka->sa.sa_handler = SIG_DFL; > ka->sa.sa_flags = 0; > +#ifdef __ARCH_HAS_SA_RESTORER > + ka->sa.sa_restorer = NULL; > +#endif
However, exec sets SIG_DFL but keeps ->sa_restorer, so probably this patch makes sense anyway.
Oleg.
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