Commit eff3860b authored by Matthew Wilcox's avatar Matthew Wilcox
Browse files

radix tree: Don't return retry entries from lookup 



Commit 66ee620f ("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: 66ee620f ("idr: Permit any valid kernel pointer to be stored")
Reported-by: default avatarGreg Kurz <groug@kaod.org>
Signed-off-by: default avatarMatthew Wilcox <willy@infradead.org>
parent cf76c364

lib/radix-tree.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

	}

tools/testing/radix-tree/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

tools/testing/radix-tree/main.c

+1 −0
Original line number Diff line number Diff line
@@ -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);

tools/testing/radix-tree/regression.h

+1 −0
Original line number Diff line number Diff line
@@ -5,5 +5,6 @@ 
void regression1_test(void);

void regression2_test(void);

void regression3_test(void);

void regression4_test(void);



#endif

tools/testing/radix-tree/regression4.c

0 → 100644
+79 −0
Original line number Diff line number Diff line 
// 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");

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE