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Date: Wed, 16 Jul 2014 14:57:20 -0700 From: Kees Cook <keescook@...omium.org> To: Andy Lutomirski <luto@...capital.net> Cc: LKML <linux-kernel@...r.kernel.org>, Will Drewry <wad@...omium.org>, James Morris <james.l.morris@...cle.com>, Oleg Nesterov <oleg@...hat.com>, "x86@...nel.org" <x86@...nel.org>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, Linux MIPS Mailing List <linux-mips@...ux-mips.org>, linux-arch <linux-arch@...r.kernel.org>, linux-security-module <linux-security-module@...r.kernel.org>, Alexei Starovoitov <ast@...mgrid.com> Subject: Re: [PATCH 5/7] x86: Split syscall_trace_enter into two phases On Wed, Jul 16, 2014 at 2:15 PM, Andy Lutomirski <luto@...capital.net> wrote: > On Wed, Jul 16, 2014 at 1:21 PM, Kees Cook <keescook@...omium.org> wrote: >> On Tue, Jul 15, 2014 at 12:32 PM, Andy Lutomirski <luto@...capital.net> wrote: >>> >>> + >>> + ret = seccomp_phase1(&sd); >>> + if (ret == SECCOMP_PHASE1_SKIP) { >>> + regs->orig_ax = -ENOSYS; >> >> Before, seccomp didn't touch orig_ax on a skip. I don't see any >> problem with this, and it's probably more clear this way, but are you >> sure there aren't unexpected side-effects from this? > > It's necessary to cause the syscall to be skipped -- see syscall_trace_enter. > > That being said, setting it to -ENOSYS is nonsense and probably > confused you at least as much as it confused me. It should be > regs->orig_ax = -1. Yes, I think that would be better. -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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