Commit 43e33924 authored by Yihao Wu's avatar Yihao Wu Committed by Chuck Lever
Browse files

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: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarYihao Wu <wuyihao@linux.alibaba.com>
Reviewed-by: default avatarNeilBrown <neilb@suse.de>
[ cel: removed unused variable ]
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent e1e8399e

net/sunrpc/cache.c

+3 −2
Original line number Diff line number Diff line
@@ -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);