Messages in this thread | | | Date | Wed, 28 Nov 2018 02:27:53 +0300 | From | "Dmitry V. Levin" <> | Subject | Re: [RFC PATCH RESEND v3 3/3] ptrace: add PTRACE_EVENT_SECCOMP support to PTRACE_GET_SYSCALL_INFO |
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On Tue, Nov 27, 2018 at 01:31:17PM +0100, Oleg Nesterov wrote: > On 11/27, Elvira Khabirova wrote: > > On Mon, 26 Nov 2018 15:35:24 +0100, Oleg Nesterov wrote: > > > On 11/25, Elvira Khabirova wrote: > > > > > > > > Extend PTRACE_GET_SYSCALL_INFO to support PTRACE_EVENT_SECCOMP stops. > > > > The information returned is the same as for syscall-enter-stops. > > > > > > Oh, this is not nice ;) there must be a better option, I hope... Plus > > > > > > > > > Can't ptrace_get_syscall() check > > > > > > child->exit_code == (PTRACE_EVENT_SECCOMP << 8) | SIGTRAP; > > > > > > to detect the PTRACE_EVENT_SECCOMP case? > > > > Nope; looks like exit_code is zeroed after wait(). > > Yes, thanks for correcting me, > > but we can use child->last_siginfo->si_code.
Yes, this approach works, thanks!
> Just like ptrace_request(PTRACE_LISTEN) > does but you can do this lockless (no need to lock_task_sighand()).
Why this can be done lockless? All other places in that file do the locking, so I'd rather add a comment in the new code.
> And if we require that the user of ptrace_get_syscall() should also use TRACESYSGOOD > then ptrace_get_syscall() can probably do something like > > int entry; > > if (!child->last_siginfo) > return -EINVAL; > else if (child->last_siginfo->si_code == (PTRACE_EVENT_SECCOMP << 8) | SIGTRAP) > entry = 1; > else if (child->last_siginfo->si_code == SIGTRAP | 0x80) > entry = child->ptrace_message == PTRACE_EVENTMSG_SYSCALL_ENTRY; > else > return -EINVAL; > > and this way PTRACE_EVENTMSG_SYSCALL_ENTRY/EXIT can't confict with seccomp or > anything else. > > No? > > Of course, debugger can do PTRACE_SETSIGINFO and confuse itself but probably we > do not care?
The only potential issue I could think of is whether PTRACE_SETSIGINFO could be used this way to cause an information leak by making PTRACE_GET_SYSCALL_INFO access some unrelated data.
-- ldv [unhandled content-type:application/pgp-signature] | |