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

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Date:   Thu, 28 Jan 2021 19:43:26 +0800
From:   Aili Yao <yaoaili@...gsoft.com>
To:     <x86@...nel.org>, <tony.luck@...el.com>, <naoya.horiguchi@....com>
CC:     <linux-kernel@...r.kernel.org>, <yangfeng1@...gsoft.com>
Subject: [PATCH] x86/fault: Send SIGBUS to user process always for hwpoison
 page access.

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@...gsoft.com>
Signed-off-by: Aili Yao <yaoaili@...gsoft.com>
---
 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