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Bruce Fields" , stable@kernel.org Subject: [PATCH 3.18 05/86] sunrpc: dont mark uninitialised items as VALID. Date: Wed, 15 May 2019 12:54:42 +0200 Message-Id: <20190515090643.489678828@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190515090642.339346723@linuxfoundation.org> References: <20190515090642.339346723@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: NeilBrown commit d58431eacb226222430940134d97bfd72f292fcd upstream. 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: 4ecd55ea0742 ("sunrpc: fix cache_head leak due to queued request") Signed-off-by: NeilBrown Signed-off-by: J. Bruce Fields Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/cache.c | 3 +++ 1 file changed, 3 insertions(+) --- a/net/sunrpc/cache.c +++ b/net/sunrpc/cache.c @@ -50,6 +50,7 @@ static void cache_init(struct cache_head 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); static void cache_fresh_unlocked(struct cache_head *head, struct cache_detail *detail); @@ -98,6 +99,8 @@ struct cache_head *sunrpc_cache_lookup(s *hp = tmp->next; tmp->next = NULL; detail->entries --; + if (cache_is_valid(tmp) == -EAGAIN) + set_bit(CACHE_NEGATIVE, &tmp->flags); cache_fresh_locked(tmp, 0); freeme = tmp; break;