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Message-ID: <20120522210704.GK11775@ZenIV.linux.org.uk> Date: Tue, 22 May 2012 22:07:05 +0100 From: Al Viro <viro@...IV.linux.org.uk> To: Will Drewry <wad@...omium.org> Cc: "H. Peter Anvin" <hpa@...or.com>, Indan Zupancic <indan@....nu>, Roland McGrath <mcgrathr@...gle.com>, Eric Paris <netdev@...isplace.org>, linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org, kernel-hardening@...ts.openwall.com, mingo@...hat.com, oleg@...hat.com, peterz@...radead.org, rdunlap@...otime.net, tglx@...utronix.de, luto@....edu, eparis@...hat.com, serge.hallyn@...onical.com, pmoore@...hat.com, akpm@...ux-foundation.org, corbet@....net, eric.dumazet@...il.com, markus@...omium.org, coreyb@...ux.vnet.ibm.com, keescook@...omium.org Subject: Re: seccomp and ptrace. what is the correct order? On Tue, May 22, 2012 at 03:48:40PM -0500, Will Drewry wrote: > On Tue, May 22, 2012 at 3:34 PM, H. Peter Anvin <hpa@...or.com> wrote: > > The proposed patch seems to duplicate the functionality in > > <asm/syscall.h>. ?Those macros also try to do the right thing in the > > presence of compat. > > That was my first thought too, so I ran a few simple tests. gcc isn't > smart enough to not add ~344 bytes of code to get the number and > arguments for the x86/kernel/ptrace.c case I included (in the > naive-est of integrations). But I don't know that it justifies the > extra patchwork or enforcing shared code across arches. > > Regardless, the syscall entry + trace code can use some attention > across the architectures. I don't know that > one-more-layer-of-abstraction is the right answer (rather than just > fixing the code). The biggest benefit would be having one-true > syscall_trace_entry slow path. That said, the fast paths will be > forever divergent so the opportunity for bugs like the ones pointed > out will still be there. FWIW, I'd prefer to have all that done inside __audit_syscall_entry(), with context->arch = syscall_get_arch(current, regs); context->major = syscall_get_nr(current, regs); syscall_get_arguments(current, regs, 0, 4, context->argv); done instead of initializations from arguments we are doing there now. I seriously doubt that it would lead to worse code than what we currently have. If nothing else, we won't be passing that pile of arguments around. And yes, asm/syscall.h stuff is probably the right approach here. For biarch ones syscall_get_arguments() is saner than doing them one by one...
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