From eff3860bbfedbac6edac57fb0d7f3a60e860c1c3 Mon Sep 17 00:00:00 2001
From: Matthew Wilcox <willy@infradead.org>
Date: Thu, 6 Dec 2018 08:19:13 -0500
Subject: [PATCH] radix tree: Don't return retry entries from lookup
Commit 66ee620f06f9 ("idr: Permit any valid kernel pointer to be stored")
changed the radix tree lookup so that it stops when reaching the bottom
of the tree. However, the condition was added in the wrong place,
making it possible to return retry entries to the caller. Reorder the
tests to check for the retry entry before checking whether we're at the
bottom of the tree. The retry entry should never be found in the tree
root, so it's safe to defer the check until the end of the loop.
Add a regression test to the test-suite to be sure this doesn't come
back.
Fixes: 66ee620f06f9 ("idr: Permit any valid kernel pointer to be stored")
Reported-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
lib/radix-tree.c | 4 +-
tools/testing/radix-tree/Makefile | 1 +
tools/testing/radix-tree/main.c | 1 +
tools/testing/radix-tree/regression.h | 1 +
tools/testing/radix-tree/regression4.c | 79 ++++++++++++++++++++++++++
5 files changed, 84 insertions(+), 2 deletions(-)
create mode 100644 tools/testing/radix-tree/regression4.c
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 1106bb6aa01e9..14d51548bea64 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -784,11 +784,11 @@ void *__radix_tree_lookup(const struct radix_tree_root *root,
while (radix_tree_is_internal_node(node)) {
unsigned offset;
- if (node == RADIX_TREE_RETRY)
- goto restart;
parent = entry_to_node(node);
offset = radix_tree_descend(parent, &node, index);
slot = parent->slots + offset;
+ if (node == RADIX_TREE_RETRY)
+ goto restart;
if (parent->shift == 0)
break;
}
diff --git a/tools/testing/radix-tree/Makefile b/tools/testing/radix-tree/Makefile
index acf1afa01c5b9..397d6b612502d 100644
--- a/tools/testing/radix-tree/Makefile
+++ b/tools/testing/radix-tree/Makefile
@@ -7,6 +7,7 @@ LDLIBS+= -lpthread -lurcu
TARGETS = main idr-test multiorder xarray
CORE_OFILES := xarray.o radix-tree.o idr.o linux.o test.o find_bit.o bitmap.o
OFILES = main.o $(CORE_OFILES) regression1.o regression2.o regression3.o \
+ regression4.o \
tag_check.o multiorder.o idr-test.o iteration_check.o benchmark.o
ifndef SHIFT
diff --git a/tools/testing/radix-tree/main.c b/tools/testing/radix-tree/main.c
index 77a44c54998f0..7a22d6e3732e5 100644
--- a/tools/testing/radix-tree/main.c
+++ b/tools/testing/radix-tree/main.c
@@ -308,6 +308,7 @@ int main(int argc, char **argv)
regression1_test();
regression2_test();
regression3_test();
+ regression4_test();
iteration_test(0, 10 + 90 * long_run);
iteration_test(7, 10 + 90 * long_run);
single_thread_tests(long_run);
diff --git a/tools/testing/radix-tree/regression.h b/tools/testing/radix-tree/regression.h
index 3c8a1584e9ee4..135145af18b7c 100644
--- a/tools/testing/radix-tree/regression.h
+++ b/tools/testing/radix-tree/regression.h
@@ -5,5 +5,6 @@
void regression1_test(void);
void regression2_test(void);
void regression3_test(void);
+void regression4_test(void);
#endif
diff --git a/tools/testing/radix-tree/regression4.c b/tools/testing/radix-tree/regression4.c
new file mode 100644
index 0000000000000..cf4e5aba6b082
--- /dev/null
+++ b/tools/testing/radix-tree/regression4.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/slab.h>
+#include <linux/radix-tree.h>
+#include <linux/rcupdate.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <assert.h>
+
+#include "regression.h"
+
+static pthread_barrier_t worker_barrier;
+static int obj0, obj1;
+static RADIX_TREE(mt_tree, GFP_KERNEL);
+
+static void *reader_fn(void *arg)
+{
+ int i;
+ void *entry;
+
+ rcu_register_thread();
+ pthread_barrier_wait(&worker_barrier);
+
+ for (i = 0; i < 1000000; i++) {
+ rcu_read_lock();
+ entry = radix_tree_lookup(&mt_tree, 0);
+ rcu_read_unlock();
+ if (entry != &obj0) {
+ printf("iteration %d bad entry = %p\n", i, entry);
+ abort();
+ }
+ }
+
+ rcu_unregister_thread();
+
+ return NULL;
+}
+
+static void *writer_fn(void *arg)
+{
+ int i;
+
+ rcu_register_thread();
+ pthread_barrier_wait(&worker_barrier);
+
+ for (i = 0; i < 1000000; i++) {
+ radix_tree_insert(&mt_tree, 1, &obj1);
+ radix_tree_delete(&mt_tree, 1);
+ }
+
+ rcu_unregister_thread();
+
+ return NULL;
+}
+
+void regression4_test(void)
+{
+ pthread_t reader, writer;
+
+ printv(1, "regression test 4 starting\n");
+
+ radix_tree_insert(&mt_tree, 0, &obj0);
+ pthread_barrier_init(&worker_barrier, NULL, 2);
+
+ if (pthread_create(&reader, NULL, reader_fn, NULL) ||
+ pthread_create(&writer, NULL, writer_fn, NULL)) {
+ perror("pthread_create");
+ exit(1);
+ }
+
+ if (pthread_join(reader, NULL) || pthread_join(writer, NULL)) {
+ perror("pthread_join");
+ exit(1);
+ }
+
+ printv(1, "regression test 4 passed\n");
+}
--
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