radix-tree tests: add regression3 test

After calling radix_tree_iter_retry(), 'slot' will be set to NULL.  This
can cause radix_tree_next_slot() to dereference the NULL pointer.  Add
Konstantin Khlebnikov's test to the regression framework.
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
Reported-by: Konstantin Khlebnikov <koct9i@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

tools/testing/radix-tree/Makefile

@@ -3,7 +3,7 @@ CFLAGS += -I. -g -Wall -D_LGPL_SOURCE
 LDFLAGS += -lpthread -lurcu
 TARGETS = main
 OFILES = main.o radix-tree.o linux.o test.o tag_check.o find_next_bit.o \
-	 regression1.o regression2.o
+	 regression1.o regression2.o regression3.o
 
 targets: $(TARGETS)
 

tools/testing/radix-tree/linux/kernel.h

@@ -13,6 +13,7 @@
 
 #define BUG_ON(expr)	assert(!(expr))
 #define __init
+#define __must_check
 #define panic(expr)
 #define printk printf
 #define __force

tools/testing/radix-tree/main.c

@@ -261,6 +261,7 @@ int main(void)
 
 	regression1_test();
 	regression2_test();
+	regression3_test();
 	single_thread_tests();
 
 	sleep(1);

tools/testing/radix-tree/regression.h

@@ -3,5 +3,6 @@
 
 void regression1_test(void);
 void regression2_test(void);
+void regression3_test(void);
 
 #endif

tools/testing/radix-tree/regression3.c

+/*
+ * Regression3
+ * Description:
+ * Helper radix_tree_iter_retry resets next_index to the current index.
+ * In following radix_tree_next_slot current chunk size becomes zero.
+ * This isn't checked and it tries to dereference null pointer in slot.
+ *
+ * Running:
+ * This test should run to completion immediately. The above bug would
+ * cause it to segfault.
+ *
+ * Upstream commit:
+ * Not yet
+ */
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/slab.h>
+#include <linux/radix-tree.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "regression.h"
+
+void regression3_test(void)
+{
+	RADIX_TREE(root, GFP_KERNEL);
+	void *ptr = (void *)4ul;
+	struct radix_tree_iter iter;
+	void **slot;
+	bool first;
+
+	printf("running regression test 3 (should take milliseconds)\n");
+
+	radix_tree_insert(&root, 0, ptr);
+	radix_tree_tag_set(&root, 0, 0);
+
+	first = true;
+	radix_tree_for_each_tagged(slot, &root, &iter, 0, 0) {
+//		printk("tagged %ld %p\n", iter.index, *slot);
+		if (first) {
+			radix_tree_insert(&root, 1, ptr);
+			radix_tree_tag_set(&root, 1, 0);
+			first = false;
+		}
+		if (radix_tree_deref_retry(*slot)) {
+//			printk("retry %ld\n", iter.index);
+			slot = radix_tree_iter_retry(&iter);
+			continue;
+		}
+	}
+	radix_tree_delete(&root, 1);
+
+	first = true;
+	radix_tree_for_each_slot(slot, &root, &iter, 0) {
+//		printk("slot %ld %p\n", iter.index, *slot);
+		if (first) {
+			radix_tree_insert(&root, 1, ptr);
+			first = false;
+		}
+		if (radix_tree_deref_retry(*slot)) {
+//			printk("retry %ld\n", iter.index);
+			slot = radix_tree_iter_retry(&iter);
+			continue;
+		}
+	}
+	radix_tree_delete(&root, 1);
+
+	first = true;
+	radix_tree_for_each_contig(slot, &root, &iter, 0) {
+//		printk("contig %ld %p\n", iter.index, *slot);
+		if (first) {
+			radix_tree_insert(&root, 1, ptr);
+			first = false;
+		}
+		if (radix_tree_deref_retry(*slot)) {
+//			printk("retry %ld\n", iter.index);
+			slot = radix_tree_iter_retry(&iter);
+			continue;
+		}
+	}
+
+	radix_tree_delete(&root, 0);
+	radix_tree_delete(&root, 1);
+
+	printf("regression test 3 passed\n");
+}