Messages in this thread | | | Date | Tue, 12 Aug 2014 15:57:25 +0900 | From | AKASHI Takahiro <> | Subject | Re: [PATCH v5 3/3] arm64: Add seccomp support |
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Will,
On 08/11/2014 06:24 PM, Will Deacon wrote: > On Fri, Aug 08, 2014 at 08:35:42AM +0100, AKASHI Takahiro wrote: >> On 08/06/2014 12:08 AM, Kees Cook wrote: >>> On Fri, Jul 25, 2014 at 2:37 AM, AKASHI Takahiro >>> <takahiro.akashi@linaro.org> wrote: >>>> I found a bug in my current patch (v5). When 32-bit tracer skips a system call, >>>> we should not update syscallno from x8 since syscallno is re-written directly >>>> via ptrace(PTRACE_SET_SYSCALL). >>> >>> Ah, yes. Will aarch64 have a PTRACE_SET_SYSCALL option, or is this >>> strictly a 32-bit vs 64-bit issue? >> >> As discussed in a few weeks ago, aarch64 won't support PTRACE_SET_SYSCALL. > > Well, I don't think anything was set in stone. If you have a compelling > reason why adding the new request gives you something over setting w8 > directly, then we can extend ptrace.
Yeah, I think I may have to change my mind. Looking into __secure_computing(), I found the code below:
> case SECCOMP_MODE_FILTER: > case SECCOMP_RET_TRACE: > ... > if (syscall_get_nr(current, regs) < 0) > goto skip;
This implies that we should modify syscallno *before* __secure_computing() returns.
I assumed, in my next version, we could skip a system call by overwriting syscallno with x8 in syscall_trace_enter() after __secure_computing() returns 0, and it actually works. But we'd better implement PTRACE_SET_SYSCALL to comply with what __secure_computing() expects.
-Takahiro AKASHI
> Will > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
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