fix potential race condition in DefaultResolver when discard_cache() #698
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delete_all() and recycle() is not atomic; and there may be read-write race as well.
Coldwings
reviewed
Jan 20, 2025
| @@ -304,6 +300,7 @@ class DefaultResolver : public Resolver { | |||
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| void discard_cache(const char *host, IPAddr ip) override { | |||
| auto ipaddr = dnscache_.borrow(host); | |||
| scoped_rwlock _(*ipaddr, WLOCK); | |||
| if (ip.undefined() || ipaddr->empty()) { | |||
| ipaddr->delete_all(); | |||
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recycle will destruct ipaddrlist so do not need to delete items right here, and also do not need a write lock in such condition.
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delete_all() and recycle() is not atomic; and there may be read-write race as well.