--- zzzz-none-000/linux-2.6.39.4/arch/x86/kernel/dumpstack_32.c	2011-08-03 19:43:28.000000000 +0000
+++ puma6-arm-6490-729/linux-2.6.39.4/arch/x86/kernel/dumpstack_32.c	2021-11-10 13:23:10.000000000 +0000
@@ -13,6 +13,7 @@
 #include <linux/sysfs.h>
 #include <linux/bug.h>
 #include <linux/nmi.h>
+#include <linux/mm.h>
 
 #include <asm/stacktrace.h>
 
@@ -81,8 +82,20 @@
 	show_trace_log_lvl(task, regs, sp, bp, log_lvl);
 }
 
+/*
+ * On old kernels (pre-v3.3 at least), nested NMIs are not handled correctly.
+ * In an NMI handler, triggering a page fault allows nested NMIs to happen, so
+ * this must be avoided.  Since vmalloc'ed memory can go away anytime, we
+ * better not access it from nmi context.
+ */
+#define probe_kernel_address_nmisafe(addr, c)			\
+	({							\
+		in_nmi() && !virt_addr_valid(addr) ?		\
+			-EFAULT :				\
+			probe_kernel_address((addr), c);	\
+	})
 
-void show_registers(struct pt_regs *regs)
+void show_regs(struct pt_regs *regs)
 {
 	int i;
 
@@ -108,15 +121,21 @@
 		printk(KERN_EMERG "Code: ");
 
 		ip = (u8 *)regs->ip - code_prologue;
-		if (ip < (u8 *)PAGE_OFFSET || probe_kernel_address(ip, c)) {
+		if (ip < (u8 *)PAGE_OFFSET ||
+				probe_kernel_address_nmisafe(ip, c)) {
 			/* try starting at IP */
 			ip = (u8 *)regs->ip;
 			code_len = code_len - code_prologue + 1;
 		}
 		for (i = 0; i < code_len; i++, ip++) {
+			bool bad_probe = false;
+
 			if (ip < (u8 *)PAGE_OFFSET ||
-					probe_kernel_address(ip, c)) {
-				printk(" Bad EIP value.");
+					(bad_probe = probe_kernel_address_nmisafe(ip, c))) {
+				if (bad_probe && in_nmi())
+					printk(" Unsafe EIP address.");
+				else
+					printk(" Bad EIP value.");
 				break;
 			}
 			if (ip == (u8 *)regs->ip)