On Wed, Mar 11, 2015 at 2:43 PM, Mikael Pettersson <[email protected]> wrote: > Jann Horn writes: > > Or should I throw this patch away and write a patch > > for the prctl() manpage instead that documents that > > being able to call sigreturn() implies being able to > > effectively call sigprocmask(), at least on some > > architectures like X86? > > Well, that is the semantics of sigreturn(). It is essentially > setcontext() [which includes the actions of sigprocmask()], but > with restrictions on parameter placement (at least on x86). > > You could introduce some setting to restrict that aspect for > seccomp processes, but you can't change this for normal processes > without breaking things.
Which leads to the interesting question: does anyone ever call sigreturn with a different signal mask than the kernel put there during signal delivery or, even more strangely, with a totally made up context? I suspect that the former does happen, even if the latter may be rare or completely implausible. I certainly have code that modifies GPRs in the context prior to sigreturn. --Andy -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
