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cmap, classifier: Avoid unsafe aliasing in iterators.

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CMAP_FOR_EACH and CLS_FOR_EACH and their variants tried to use void ** as
a "pointer to any kind of pointer".  That is a violation of the aliasing
rules in ISO C which technically yields undefined behavior.  With GCC 4.1,
it causes both warnings and actual misbehavior.  One option would to add
-fno-strict-aliasing to the compiler flags, but that would only help with
GCC; who knows whether this can be worked around with other compilers.

Instead, this commit rewrites the iterators to avoid disallowed pointer
aliasing.

VMware-BZ: #1287651
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>
This commit is contained in:
Ben Pfaff
2014-07-21 21:00:04 -07:00
parent 480cda3a4a
commit 78c8df129c
9 changed files with 112 additions and 158 deletions
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69
lib/classifier.h
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@@ -1,5 +1,5 @@
/*
* Copyright (c) 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
* Copyright (c) 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
@@ -316,63 +316,40 @@ struct cls_cursor {
const struct cls_rule *target;
struct cmap_cursor subtables;
struct cmap_cursor rules;
struct cls_rule *rule;
bool safe;
};
/* Iteration requires mutual exclusion of writers. We do this by taking
* a mutex for the duration of the iteration, except for the
* 'SAFE' variant, where we release the mutex for the body of the loop. */
struct cls_cursor cls_cursor_init(const struct classifier *cls,
const struct cls_rule *target,
void **pnode, const void *offset, bool safe);
struct cls_cursor cls_cursor_start(const struct classifier *cls,
const struct cls_rule *target,
bool safe);
struct cls_rule *cls_cursor_next(struct cls_cursor *cursor,
const struct cls_rule *);
#define CLS_CURSOR_START(RULE, MEMBER, CLS, TARGET) \
cls_cursor_init(CLS, (TARGET), (void **)&(RULE), \
OBJECT_CONTAINING(NULL, RULE, MEMBER), false)
#define CLS_CURSOR_START_SAFE(RULE, MEMBER, CLS, TARGET) \
cls_cursor_init(CLS, (TARGET), (void **)&(RULE), \
OBJECT_CONTAINING(NULL, RULE, MEMBER), true)
#define CLS_FOR_EACH(RULE, MEMBER, CLS) \
for (struct cls_cursor cursor__ = CLS_CURSOR_START(RULE, MEMBER, CLS, \
NULL); \
RULE != OBJECT_CONTAINING(NULL, RULE, MEMBER); \
ASSIGN_CONTAINER(RULE, cls_cursor_next(&cursor__, &(RULE)->MEMBER), \
MEMBER))
void cls_cursor_advance(struct cls_cursor *);
#define CLS_FOR_EACH(RULE, MEMBER, CLS) \
CLS_FOR_EACH_TARGET(RULE, MEMBER, CLS, NULL)
#define CLS_FOR_EACH_TARGET(RULE, MEMBER, CLS, TARGET) \
for (struct cls_cursor cursor__ = CLS_CURSOR_START(RULE, MEMBER, CLS, \
TARGET); \
RULE != OBJECT_CONTAINING(NULL, RULE, MEMBER); \
ASSIGN_CONTAINER(RULE, cls_cursor_next(&cursor__, &(RULE)->MEMBER), \
MEMBER))
/* This form allows classifier_remove() to be called within the loop. */
#define CLS_FOR_EACH_SAFE(RULE, NEXT, MEMBER, CLS) \
for (struct cls_cursor cursor__ = CLS_CURSOR_START_SAFE(RULE, MEMBER, \
CLS, NULL); \
(RULE != OBJECT_CONTAINING(NULL, RULE, MEMBER) \
? ASSIGN_CONTAINER(NEXT, cls_cursor_next(&cursor__, \
&(RULE)->MEMBER), \
MEMBER), true \
for (struct cls_cursor cursor__ = cls_cursor_start(CLS, TARGET, false); \
(cursor__.rule \
? (ASSIGN_CONTAINER(RULE, cursor__.rule, MEMBER), \
true) \
: false); \
(RULE) = (NEXT))
cls_cursor_advance(&cursor__))
/* This form allows classifier_remove() to be called within the loop. */
#define CLS_FOR_EACH_TARGET_SAFE(RULE, NEXT, MEMBER, CLS, TARGET) \
for (struct cls_cursor cursor__ = CLS_CURSOR_START_SAFE(RULE, MEMBER, \
CLS, TARGET); \
(RULE != OBJECT_CONTAINING(NULL, RULE, MEMBER) \
? ASSIGN_CONTAINER(NEXT, cls_cursor_next(&cursor__, \
&(RULE)->MEMBER), \
MEMBER), true \
/* These forms allows classifier_remove() to be called within the loop. */
#define CLS_FOR_EACH_SAFE(RULE, MEMBER, CLS) \
CLS_FOR_EACH_TARGET_SAFE(RULE, MEMBER, CLS, NULL)
#define CLS_FOR_EACH_TARGET_SAFE(RULE, MEMBER, CLS, TARGET) \
for (struct cls_cursor cursor__ = cls_cursor_start(CLS, TARGET, true); \
(cursor__.rule \
? (ASSIGN_CONTAINER(RULE, cursor__.rule, MEMBER), \
cls_cursor_advance(&cursor__), \
true) \
: false); \
(RULE) = (NEXT))
) \
#ifdef __cplusplus
}