On Mon, 8 Mar 2021 11:00:28 -0800
Andy Lutomirski [off-list ref] wrote:

quoted

On Mar 8, 2021, at 10:31 AM, Luck, Tony [off-list ref] wrote:

  

quoted

Can you point me at that SIGBUS code in a current kernel?  

It is in kill_me_maybe().  mce_vaddr is setup when we disassemble whatever get_user()
or copy from user variant was in use in the kernel when the poison memory was consumed.

       if (p->mce_vaddr != (void __user *)-1l) {
               force_sig_mceerr(BUS_MCEERR_AR, p->mce_vaddr, PAGE_SHIFT);  

Hmm. On the one hand, no one has complained yet. On the other hand, hardware that supports this isn’t exactly common.

We may need some actual ABI design here. We also need to make sure that things like io_uring accesses or, more generally, anything using the use_mm / use_temporary_mm ends up either sending no signal or sending a signal to the right target.

quoted

Would it be any better if we used the BUS_MCEERR_AO code that goes into siginfo?  

Dunno.

I have one thought here but don't know if it's proper:

Previous patch use force_sig_mceerr to the user process for such a scenario; with this method
The SIGBUS can't be ignored as force_sig_mceerr() was designed to.

If the user process don't want this signal, will it set signal config to ignore?
Maybe we can use a send_sig_mceerr() instead of force_sig_mceerr(), if process want to
ignore the SIGBUS, then it will ignore that, or it can also process the SIGBUS?

-- 
Thanks!
Aili Yao