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Date: Tue, 24 Nov 2020 15:08:49 -0800 From: Andy Lutomirski <luto@...nel.org> To: Dmitry Safonov <dima@...sta.com> Cc: LKML <linux-kernel@...r.kernel.org>, Dmitry Safonov <0x7f454c46@...il.com>, Alexander Viro <viro@...iv.linux.org.uk>, Andrew Morton <akpm@...ux-foundation.org>, Andy Lutomirski <luto@...nel.org>, Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>, Catalin Marinas <catalin.marinas@....com>, Christophe Leroy <christophe.leroy@...roup.eu>, Guo Ren <guoren@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>, Oleg Nesterov <oleg@...hat.com>, Russell King <linux@...linux.org.uk>, Thomas Bogendoerfer <tsbogend@...ha.franken.de>, Thomas Gleixner <tglx@...utronix.de>, Vincenzo Frascino <vincenzo.frascino@....com>, Will Deacon <will@...nel.org>, X86 ML <x86@...nel.org> Subject: Re: [PATCH v2 12/19] x86/signal: Land on &frame->retcode when vdso isn't mapped On Mon, Nov 23, 2020 at 4:30 PM Dmitry Safonov <dima@...sta.com> wrote: > > Since commit 9fbbd4dd17d0 ("x86: Don't require the vDSO for handling > a.out signals") after processing 32-bit signal if there is no vdso > mapped frame->retcode is used as a landing. > Do the same for rt ia32 signals. > It also makes the ia32 compat signals match the native ia32 case. > > This shouldn't be mistaken for encouragement for running binaries with > executable stack, rather something to do in hopefully very rare > situation with disabled or unmapped vdso and absent SA_RESTORER. > For non-executable stack it'll segfault on attempt to land, rather than > land on a random address where vdso was previously mapped. > For programs with executable stack it'll just do the same for rt signals > as for non-rt. > > Discouraging users to run with executable stack is done separately in > commit 47a2ebb7f505 ("execve: warn if process starts with executable > stack"). > > Signed-off-by: Dmitry Safonov <dima@...sta.com> The new code is more readable than the old code, too. Acked-by: Andy Lutomirski <luto@...nel.org>
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