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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 <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>
This commit is contained in:
Yihao Wu 2020-04-06 01:57:22 +08:00 committed by Chuck Lever
parent e1e8399eee
commit 43e33924c3
1 changed files with 3 additions and 2 deletions
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5
net/sunrpc/cache.c
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@ -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);