sunrpc: fix cache_head leak due to queued request
authorVasily Averin <vvs@virtuozzo.com>
Wed, 28 Nov 2018 08:45:57 +0000 (11:45 +0300)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sun, 13 Jan 2019 09:01:02 +0000 (10:01 +0100)
commit76da01793fbdcac42d9828b778cfa0d63d27bfac
treec54db2b537806043724e8cc0ecec97c0ea799020
parent89b03877088751fc44dd93d40fdcd74a04927c45
sunrpc: fix cache_head leak due to queued request

commit 4ecd55ea074217473f94cfee21bb72864d39f8d7 upstream.

After commit d202cce8963d, an expired cache_head can be removed from the
cache_detail's hash.

However, the expired cache_head may be waiting for a reply from a
previously submitted request. Such a cache_head has an increased
refcounter and therefore it won't be freed after cache_put(freeme).

Because the cache_head was removed from the hash it cannot be found
during cache_clean() and can be leaked forever, together with stalled
cache_request and other taken resources.

In our case we noticed it because an entry in the export cache was
holding a reference on a filesystem.

Fixes d202cce8963d ("sunrpc: never return expired entries in sunrpc_cache_lookup")
Cc: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Cc: stable@kernel.org # 2.6.35
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net/sunrpc/cache.c