SUNRPC/cache: Fix unsafe traverse caused double-free in cache_purge
Deleting list entry within hlist_for_each_entry_safe is not safe unless
next pointer (tmp) is protected too. It's not, because once hash_lock
is released, cache_clean may delete the entry that tmp points to. Then
cache_purge can walk to a deleted entry and tries to double free it.
Fix this bug by holding only the deleted entry's reference.
Suggested-by: NeilBrown <[email protected]>
Signed-off-by: Yihao Wu <[email protected]>
Reviewed-by: NeilBrown <[email protected]>
[ cel: removed unused variable ]
Signed-off-by: Chuck Lever <[email protected]>
diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index af0ddd2..baef5ee 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -529,7 +529,6 @@ void cache_purge(struct cache_detail *detail)
{
struct cache_head *ch = NULL;
struct hlist_head *head = NULL;
- struct hlist_node *tmp = NULL;
int i = 0;
spin_lock(&detail->hash_lock);
@@ -541,7 +540,9 @@ void cache_purge(struct cache_detail *detail)
dprintk("RPC: %d entries in %s cache\n", detail->entries, detail->name);
for (i = 0; i < detail->hash_size; i++) {
head = &detail->hash_table[i];
- hlist_for_each_entry_safe(ch, tmp, head, cache_list) {
+ while (!hlist_empty(head)) {
+ ch = hlist_entry(head->first, struct cache_head,
+ cache_list);
sunrpc_begin_cache_remove_entry(ch, detail);
spin_unlock(&detail->hash_lock);
sunrpc_end_cache_remove_entry(ch, detail);
