diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index a851f16..9bca141 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -227,10 +227,17 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
 		int allowed;
 
 		sz = size_inside_page(p, count);
+		if (IS_ENABLED(CONFIG_DEBUG_AID_FOR_SYZBOT) &&
+		    fatal_signal_pending(current))
+			printk("write_mem: sz=%zd count=%zd\n", sz, count);
 
 		allowed = page_is_allowed(p >> PAGE_SHIFT);
-		if (!allowed)
+		if (!allowed) {
+			if (IS_ENABLED(CONFIG_DEBUG_AID_FOR_SYZBOT) &&
+			    fatal_signal_pending(current))
+				printk("write_mem: written=%zd *ppos=%lld\n", written, *ppos);
 			return -EPERM;
+		}
 
 		/* Skip actual writing when a page is marked as restricted. */
 		if (allowed == 1) {
@@ -263,6 +270,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
 	}
 
 	*ppos += written;
+	if (IS_ENABLED(CONFIG_DEBUG_AID_FOR_SYZBOT) &&
+	    fatal_signal_pending(current))
+		printk("write_mem: written=%zd *ppos=%lld\n", written, *ppos);
 	return written;
 }