On Thu, 4 Feb 2021 07:25:55 +0000
HORIGUCHI NAOYA(堀口　直也) [off-list ref] wrote:

Hi Aili,

On Mon, Feb 01, 2021 at 04:17:49PM +0800, Aili Yao wrote:

quoted

When one page is already hwpoisoned by AO action, process may not be
killed, the process mapping this page may make a syscall include this
page and result to trigger a VM_FAULT_HWPOISON fault, if it's in kernel
mode it may be fixed by fixup_exception. Current code will just return
error code to user process.

This is not sufficient, we should send a SIGBUS to the process and log
the info to console, as we can't trust the process will handle the error
correctly.

Suggested-by: Feng Yang <redacted>
Signed-off-by: Aili Yao <redacted>
---  

...

quoted

@@ -662,12 +662,32 @@ no_context(struct pt_regs *regs, unsigned long error_code,
 		 * In this case we need to make sure we're not recursively
 		 * faulting through the emulate_vsyscall() logic.
 		 */
+
+		if (IS_ENABLED(CONFIG_MEMORY_FAILURE) &&
+		    fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
+			unsigned int lsb = 0;
+
+			pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
+				current->comm, current->pid, address);
+
+			sanitize_error_code(address, &error_code);
+			set_signal_archinfo(address, error_code);
+
+			if (fault & VM_FAULT_HWPOISON_LARGE)
+				lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
+			if (fault & VM_FAULT_HWPOISON)
+				lsb = PAGE_SHIFT;
+
+			force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);  

This part contains some duplicated code with do_sigbus(), so some refactoring (like
adding a common function) would be more helpful.

Yes, agree, I will modify this and rebase to the big fault series from tip.

Thanks
Aili Yao