Messages in this thread | | | Date | Tue, 30 Jun 2015 13:06:46 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH v4 02/17] x86/entry/64/compat: Fix bad fast syscall arg failure path |
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* Borislav Petkov <bp@alien8.de> wrote:
> On Mon, Jun 29, 2015 at 12:33:34PM -0700, Andy Lutomirski wrote: > > diff --git a/arch/x86/entry/entry_64_compat.S b/arch/x86/entry/entry_64_compat.S > > index bb187a6a877c..efe0b1e499fa 100644 > > --- a/arch/x86/entry/entry_64_compat.S > > +++ b/arch/x86/entry/entry_64_compat.S > > @@ -425,8 +425,39 @@ cstar_tracesys: > > END(entry_SYSCALL_compat) > > > > ia32_badarg: > > - ASM_CLAC > > - movq $-EFAULT, RAX(%rsp) > > + /* > > + * So far, we've entered kernel mode, set AC, turned on IRQs, and > > + * saved C regs except r8-r11. We haven't done any of the other > > + * standard entry work, though. We want to bail, but we shouldn't > > + * treat this as a syscall entry since we don't even know what the > > + * args are. Instead, treat this as a non-syscall entry, finish > > + * the entry work, and immediately exit after setting AX = -EFAULT. > > + * > > + * We're really just being polite here. Killing the task outright > > + * would be a reasonable action, too. Given that the only valid > > + * way to have gotten here is through the vDSO, and we already know > > + * that the stack pointer is bad, the task isn't going to survive > > + * for long no matter what we do. > > You mean something like > > force_sig_info(SIGSEGV, &si, current); > > ?
We should also emit a warning message, even if user-space installed a 'special' sigfault handler to hide such failures. (I'm looking at you systemd!)
Thanks,
Ingo
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