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libudev: replace unique list entries in place

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udev_list_entry_add() freed the existing entry for a name before inserting
its replacement. Today that cannot lose the old entry, but only because
re-adding the key that was just removed never makes the hashmap grow, which
is an internal detail of the hashmap. Use hashmap_ensure_replace() instead:
it updates the existing bucket in place, making it explicit that replacing
an entry neither allocates nor can drop the previous value under OOM.

Follow-up for c01130824f
This commit is contained in:
Luca Boccassi
2026-07-13 13:03:27 +01:00
parent 24dee4afc5
commit dcfd156705
1 changed files with 11 additions and 3 deletions
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src/libudev/libudev-list.c
+11 -3
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@@ -40,7 +40,7 @@ static struct udev_list_entry* udev_list_entry_free(struct udev_list_entry *entr
if (entry->list) {
if (entry->list->unique && entry->name)
hashmap_remove(entry->list->unique_entries, entry->name);
hashmap_remove_value(entry->list->unique_entries, entry->name, entry);
if (!entry->list->unique || entry->list->uptodate)
LIST_REMOVE(entries, entry->list->entries, entry);
@@ -90,11 +90,19 @@ struct udev_list_entry* udev_list_entry_add(struct udev_list *list, const char *
return NULL;
if (list->unique) {
udev_list_entry_free(hashmap_get(list->unique_entries, entry->name));
struct udev_list_entry *old;
if (hashmap_ensure_put(&list->unique_entries, &udev_list_entry_hash_ops, entry->name, entry) < 0)
/* Replace the entry for an already known name in a single step. hashmap_replace() reuses the
* existing bucket and hence never allocates, so an existing entry is never dropped, not even
* under memory pressure. Allocating may only fail when adding a genuinely new name, in which
* case there is nothing to lose. */
old = hashmap_get(list->unique_entries, entry->name);
if (hashmap_ensure_replace(&list->unique_entries, &udev_list_entry_hash_ops, entry->name, entry) < 0)
return NULL;
udev_list_entry_free(old);
list->uptodate = false;
} else
LIST_APPEND(entries, list->entries, entry);