Commit d58431ea authored Apr 05, 2019 by NeilBrown Committed by J. Bruce Fields Apr 05, 2019

sunrpc: don't mark uninitialised items as VALID.



A recent commit added a call to cache_fresh_locked()
when an expired item was found.
The call sets the CACHE_VALID flag, so it is important
that the item actually is valid.
There are two ways it could be valid:
1/ If ->update has been called to fill in relevant content
2/ if CACHE_NEGATIVE is set, to say that content doesn't exist.

An expired item that is waiting for an update will be neither.
Setting CACHE_VALID will mean that a subsequent call to cache_put()
will be likely to dereference uninitialised pointers.

So we must make sure the item is valid, and we already have code to do
that in try_to_negate_entry().  This takes the hash lock and so cannot
be used directly, so take out the two lines that we need and use them.

Now cache_fresh_locked() is certain to be called only on
a valid item.

Cc: stable@kernel.org # 2.6.35
Fixes: 4ecd55ea ("sunrpc: fix cache_head leak due to queued request")
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

parent 79a3aaa7

net/sunrpc/cache.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -54,6 +54,7 @@ static void cache_init(struct cache_head h, struct cache_detail detail)
		h->last_refresh = now;
		}

		static inline int cache_is_valid(struct cache_head *h);
		static void cache_fresh_locked(struct cache_head *head, time_t expiry,
		struct cache_detail *detail);
		static void cache_fresh_unlocked(struct cache_head *head,
		@@ -105,6 +106,8 @@ static struct cache_head sunrpc_cache_add_entry(struct cache_detail detail,
		if (cache_is_expired(detail, tmp)) {
		hlist_del_init_rcu(&tmp->cache_list);
		detail->entries --;
		if (cache_is_valid(tmp) == -EAGAIN)
		set_bit(CACHE_NEGATIVE, &tmp->flags);
		cache_fresh_locked(tmp, 0, detail);
		freeme = tmp;
		break;

Admin message