Re: [PATCH 1/2] arm64: Add seccomp support

[AKASHI Takahiro]

On 02/20/2014 01:41 AM, Catalin Marinas wrote:
> On Wed, Feb 19, 2014 at 11:39:09AM +0000, AKASHI Takahiro wrote:
> > On 02/19/2014 12:38 AM, Catalin Marinas wrote:
> > > On Fri, Feb 07, 2014 at 10:11:31AM +0000, AKASHI Takahiro wrote:
> > > > --- a/arch/arm64/kernel/ptrace.c
> > > > +++ b/arch/arm64/kernel/ptrace.c
> > > > @@ -26,6 +26,7 @@
> > > >    #include <linux/smp.h>
> > > >    #include <linux/ptrace.h>
> > > >    #include <linux/user.h>
> > > > +#include <linux/seccomp.h>
> > > >    #include <linux/security.h>
> > > >    #include <linux/init.h>
> > > >    #include <linux/signal.h>
> > > > @@ -1064,6 +1065,10 @@ asmlinkage int syscall_trace(int dir, struct pt_regs *regs)
> > > >    {
> > > >    	unsigned long saved_reg;
> > > >
> > > > +	if (!dir && secure_computing((int)regs->syscallno))
> > > > +		/* seccomp failures shouldn't expose any additional code. */
> > > > +		return -1;
> > >
> > > That's only restricted to the arm64 code but could we use a more
> > > meaningful error number?
> >
> > Other architectures, including arm, also return just -1 in syscall_trace_enter(),
> > but of course, we can use another value, say, -EPERM or -ENOSYS?
>
> Actually we have another case of setting regs->syscallno = ~0UL in the
> same function, so we could do the same (also in line with entry.S).

I believe that I got you now, but we need to distinguish failure case of
seccomp and the existing (~0UL) case. In former case, depending on a bpf
rule loaded into the kernel, errno may be assigned to any arbitrary number
(not necessarily ENOSYS).
So I will use another value for this specific seccomp case.

Thanks,
-Takahiro AKASHI
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