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BUG/MINOR: dict: race condition fix when inserting dictionary entries.

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When checking the result of an ebis_insert() call in an ebtree with unique keys,
if already present, in place of freeing() the old one and return the new one,
rather the correct way is to free the new one, and return the old one. For
this, the __dict_insert() function was folded into dict_insert() as this
significantly simplifies the test of duplicates.

Thanks to Olivier for having reported this bug which came with this one:
"MINOR: dict: Add dictionary new data structure".
This commit is contained in:
Frdric Lcaille 2019-06-11 08:34:26 +02:00 committed by Willy Tarreau
parent e4d7c9dd65
commit b5ecf0393c
1 changed files with 6 additions and 19 deletions
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25
src/dict.c
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@ -76,30 +76,13 @@ static struct dict_entry *__dict_lookup(struct dict *d, const char *s)
return de;
}
/*
* Insert <node> node in <root> ebtree, deleting any already existing node with
* the same value.
*/
static struct ebpt_node *__dict_insert(struct eb_root *root, struct ebpt_node *node)
{
struct ebpt_node *n;
n = ebis_insert(root, node);
if (n != node) {
ebpt_delete(n);
free_dict_entry(container_of(n, struct dict_entry, value));
ebis_insert(root, node);
}
return node;
}
/*
* Insert an entry in <d> dictionary with <s> as value. *
*/
struct dict_entry *dict_insert(struct dict *d, char *s)
{
struct dict_entry *de;
struct ebpt_node *n;
HA_RWLOCK_RDLOCK(DICT_LOCK, &d->rwlock);
de = __dict_lookup(d, s);
@ -112,8 +95,12 @@ struct dict_entry *dict_insert(struct dict *d, char *s)
return NULL;
HA_RWLOCK_WRLOCK(DICT_LOCK, &d->rwlock);
__dict_insert(&d->values, &de->value);
n = ebis_insert(&d->values, &de->value);
HA_RWLOCK_WRUNLOCK(DICT_LOCK, &d->rwlock);
if (n != &de->value) {
free_dict_entry(de);
de = container_of(n, struct dict_entry, value);
}
return de;
}