svcrpc: take lock on turning entry NEGATIVE in cache_check
We attempt to turn a cache entry negative in place. But that entry may already have been filled in by some other task since we last checked whether it was valid, so we could be modifying an already-valid entry. If nothing else there's a likely leak in such a case when the entry is eventually put() and contents are not freed because it has CACHE_NEGATIVE set. So, take the cache_lock just as sunrpc_cache_update() does. Reviewed-by: NeilBrown <neilb@suse.de> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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@ -213,6 +213,23 @@ static inline int cache_is_valid(struct cache_detail *detail, struct cache_head
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}
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}
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}
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}
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static int try_to_negate_entry(struct cache_detail *detail, struct cache_head *h)
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{
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int rv;
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write_lock(&detail->hash_lock);
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rv = cache_is_valid(detail, h);
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if (rv != -EAGAIN) {
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write_unlock(&detail->hash_lock);
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return rv;
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}
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set_bit(CACHE_NEGATIVE, &h->flags);
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cache_fresh_locked(h, seconds_since_boot()+CACHE_NEW_EXPIRY);
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write_unlock(&detail->hash_lock);
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cache_fresh_unlocked(h, detail);
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return -ENOENT;
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}
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/*
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/*
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* This is the generic cache management routine for all
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* This is the generic cache management routine for all
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* the authentication caches.
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* the authentication caches.
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@ -251,14 +268,8 @@ int cache_check(struct cache_detail *detail,
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case -EINVAL:
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case -EINVAL:
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clear_bit(CACHE_PENDING, &h->flags);
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clear_bit(CACHE_PENDING, &h->flags);
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cache_revisit_request(h);
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cache_revisit_request(h);
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if (rv == -EAGAIN) {
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rv = try_to_negate_entry(detail, h);
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set_bit(CACHE_NEGATIVE, &h->flags);
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cache_fresh_locked(h, seconds_since_boot()+CACHE_NEW_EXPIRY);
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cache_fresh_unlocked(h, detail);
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rv = -ENOENT;
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}
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break;
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break;
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case -EAGAIN:
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case -EAGAIN:
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clear_bit(CACHE_PENDING, &h->flags);
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clear_bit(CACHE_PENDING, &h->flags);
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cache_revisit_request(h);
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cache_revisit_request(h);
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