From: Yihao Wu <wuyihao@linux.alibaba.com> mainline inclusion from mainline-5.7-rc3 commit 43e33924c38e8faeb0c12035481cb150e602e39d category: bugfix bugzilla: 51810 CVE: NA ------------------------------------------------- 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 <neilb@suse.de> Signed-off-by: Yihao Wu <wuyihao@linux.alibaba.com> Reviewed-by: NeilBrown <neilb@suse.de> [ cel: removed unused variable ] Signed-off-by: Chuck Lever <chuck.lever@oracle.com> (cherry picked from commit 43e33924c38e8faeb0c12035481cb150e602e39d) Signed-off-by: Yufen Wang <wangyufen@huawei.com> Reviewed-by: Yue Haibing <yuehaibing@huawei.com> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- net/sunrpc/cache.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c index 62b2bd8e1efc5..e2d3cf801c310 100644 --- a/net/sunrpc/cache.c +++ b/net/sunrpc/cache.c @@ -487,7 +487,6 @@ 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; write_lock(&detail->hash_lock); @@ -499,7 +498,9 @@ 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); hlist_del_init(&ch->cache_list); detail->entries--; -- 2.25.1