Messages in this thread Patch in this message | | | Date | Mon, 20 Jun 2016 17:24:25 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH] x86/ptrace: Remove questionable TS_COMPAT usage in ptrace |
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On 06/19, Andy Lutomirski wrote: > > On Sat, Jun 18, 2016 at 10:02 AM, Andy Lutomirski <luto@amacapital.net> wrote: > Step 1: for 4.7 and for -stable, introduce TS_I386_REGS_POKED. Set it > in putreg32. Use it in syscall_get_error, get_nr_restart_syscall, > etc. Clear it in do_signal.
do_signal() won't be necessarily called...
> I wonder if we could actually get away with doing syscall restart > processing before ptrace invocation.
How? this doesn't look possible or I misunderstood.
How about the simple change below for now? IIRC 32-bit task can't use "syscall" so if syscall_get_nr() >= 0 then even the wrong TS_COMPAT is not that bad, even if it "leaks" to user-mode.
nobody should use, say, in_ia32_syscall() unless we know that "in syscall" is actually true. Hmm, arch/x86/kernel/uprobes.c does and this is wrong regardless, I'll send the fix.
Oleg.
--- x/arch/x86/kernel/ptrace.c +++ x/arch/x86/kernel/ptrace.c @@ -930,7 +930,7 @@ static int putreg32(struct task_struct * * exit from a 32-bit syscall with TS_COMPAT still set. */ regs->orig_ax = value; - if (syscall_get_nr(child, regs) >= 0) + if (syscall_get_nr(child, regs) >= 0 && !user_64bit_mode(regs)) task_thread_info(child)->status |= TS_COMPAT; break;
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