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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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44
lib/classifier.c
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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.
@@ -476,8 +476,8 @@ classifier_destroy(struct classifier *cls)
OVS_EXCLUDED(cls->mutex)
{
if (cls) {
struct cls_partition *partition, *next_partition;
struct cls_subtable *subtable, *next_subtable;
struct cls_partition *partition;
struct cls_subtable *subtable;
int i;
ovs_mutex_lock(&cls->mutex);
@@ -485,14 +485,12 @@ classifier_destroy(struct classifier *cls)
trie_destroy(&cls->tries[i].root);
}
CMAP_FOR_EACH_SAFE (subtable, next_subtable, cmap_node,
&cls->subtables_map) {
CMAP_FOR_EACH_SAFE (subtable, cmap_node, &cls->subtables_map) {
destroy_subtable(cls, subtable);
}
cmap_destroy(&cls->subtables_map);
CMAP_FOR_EACH_SAFE (partition, next_partition, cmap_node,
&cls->partitions) {
CMAP_FOR_EACH_SAFE (partition, cmap_node, &cls->partitions) {
ovsrcu_postpone(free, partition);
}
cmap_destroy(&cls->partitions);
@@ -1219,18 +1217,18 @@ search_subtable(const struct cls_subtable *subtable,
* such that cls_rule_is_loose_match(rule, target) returns true.
*
* Ignores target->priority. */
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)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
struct cls_cursor cursor;
struct cls_subtable *subtable;
struct cls_rule *cls_rule = NULL;
cursor.safe = safe;
cursor.cls = cls;
cursor.target = target && !cls_rule_is_catchall(target) ? target : NULL;
cursor.rule = NULL;
/* Find first rule. */
ovs_mutex_lock(&cursor.cls->mutex);
@@ -1240,14 +1238,13 @@ struct cls_cursor cls_cursor_init(const struct classifier *cls,
if (rule) {
cursor.subtable = subtable;
cls_rule = rule->cls_rule;
cursor.rule = rule->cls_rule;
break;
}
}
*pnode = (char *)cls_rule + (ptrdiff_t)offset;
/* Leave locked if requested and have a rule. */
if (safe || !cls_rule) {
if (safe || !cursor.rule) {
ovs_mutex_unlock(&cursor.cls->mutex);
}
return cursor;
@@ -1258,18 +1255,19 @@ cls_cursor_next_unlock(struct cls_cursor *cursor, struct cls_rule *rule)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
/* Release the mutex if no rule, or 'safe' mode. */
cursor->rule = rule;
if (!rule || cursor->safe) {
ovs_mutex_unlock(&cursor->cls->mutex);
}
}
/* Returns the next matching cls_rule in 'cursor''s iteration, or a null
* pointer if there are no more matches. */
struct cls_rule *
cls_cursor_next(struct cls_cursor *cursor, const struct cls_rule *rule_)
/* Sets 'cursor->rule' to the next matching cls_rule in 'cursor''s iteration,
* or to null if all matching rules have been visited. */
void
cls_cursor_advance(struct cls_cursor *cursor)
OVS_NO_THREAD_SAFETY_ANALYSIS
{
struct cls_match *rule = CONST_CAST(struct cls_match *, rule_->cls_match);
struct cls_match *rule = cursor->rule->cls_match;
const struct cls_subtable *subtable;
struct cls_match *next;
@@ -1281,7 +1279,7 @@ cls_cursor_next(struct cls_cursor *cursor, const struct cls_rule *rule_)
next = next_rule_in_list__(rule);
if (next->priority < rule->priority) {
cls_cursor_next_unlock(cursor, next->cls_rule);
return next->cls_rule;
return;
}
/* 'next' is the head of the list, that is, the rule that is included in
@@ -1291,7 +1289,7 @@ cls_cursor_next(struct cls_cursor *cursor, const struct cls_rule *rule_)
CMAP_CURSOR_FOR_EACH_CONTINUE (rule, cmap_node, &cursor->rules) {
if (rule_matches(rule, cursor->target)) {
cls_cursor_next_unlock(cursor, rule->cls_rule);
return rule->cls_rule;
return;
}
}
@@ -1301,12 +1299,12 @@ cls_cursor_next(struct cls_cursor *cursor, const struct cls_rule *rule_)
if (rule) {
cursor->subtable = subtable;
cls_cursor_next_unlock(cursor, rule->cls_rule);
return rule->cls_rule;
return;
}
}
ovs_mutex_unlock(&cursor->cls->mutex);
return NULL;
cursor->rule = NULL;
}
static struct cls_subtable *