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    Subject[PATCH 4.14 067/105] sunrpc: fix cache_head leak due to queued request
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Vasily Averin <vvs@virtuozzo.com>

    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 | 10 +++++++++-
    1 file changed, 9 insertions(+), 1 deletion(-)

    --- a/net/sunrpc/cache.c
    +++ b/net/sunrpc/cache.c
    @@ -54,6 +54,11 @@ static void cache_init(struct cache_head
    h->last_refresh = now;
    }

    +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,
    + struct cache_detail *detail);
    +
    struct cache_head *sunrpc_cache_lookup(struct cache_detail *detail,
    struct cache_head *key, int hash)
    {
    @@ -95,6 +100,7 @@ struct cache_head *sunrpc_cache_lookup(s
    if (cache_is_expired(detail, tmp)) {
    hlist_del_init(&tmp->cache_list);
    detail->entries --;
    + cache_fresh_locked(tmp, 0, detail);
    freeme = tmp;
    break;
    }
    @@ -110,8 +116,10 @@ struct cache_head *sunrpc_cache_lookup(s
    cache_get(new);
    write_unlock(&detail->hash_lock);

    - if (freeme)
    + if (freeme) {
    + cache_fresh_unlocked(freeme, detail);
    cache_put(freeme, detail);
    + }
    return new;
    }
    EXPORT_SYMBOL_GPL(sunrpc_cache_lookup);

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