[PATCH] x86/fault: Send SIGBUS to user process always for hwpoison page access.

[Aili Yao]

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, as 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 suffient, 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 <yangfeng1@xxxxxxxxxxxx>
Signed-off-by: Aili Yao <yaoaili@xxxxxxxxxxxx>
---
 arch/x86/mm/fault.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index f1f1b5a0956a..36d1e385512b 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -662,7 +662,16 @@ 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.
 		 */
+#ifdef CONFIG_MEMORY_FAILURE
+		if (si_code == BUS_MCEERR_AR && signal == SIGBUS)
+			pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
+				current->comm, current->pid, address);
+
+		if ((current->thread.sig_on_uaccess_err && signal) ||
+			(si_code == BUS_MCEERR_AR && signal == SIGBUS)) {
+#else
 		if (current->thread.sig_on_uaccess_err && signal) {
+#endif
 			sanitize_error_code(address, &error_code);
 
 			set_signal_archinfo(address, error_code);
@@ -927,7 +936,14 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
 {
 	/* Kernel mode? Handle exceptions or die: */
 	if (!(error_code & X86_PF_USER)) {
+#ifdef CONFIG_MEMORY_FAILURE
+		if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE))
+			no_context(regs, error_code, address, SIGBUS, BUS_MCEERR_AR);
+		else
+			no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
+#else
 		no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
+#endif
 		return;
 	}
 
-- 
2.25.1