From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A3DC1BA48 for ; Tue, 7 Mar 2023 18:26:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0E5FCC433EF; Tue, 7 Mar 2023 18:26:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1678213584; bh=R8WZzBbrGpBQq+SGjS+yP1mOYgU01k+VqiIedrTi4js=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VXL+vFlx5WeQZ/eW9z+i06uy4U5a/NfEMqb9DAdzvaAfc07vknm2coWntbbvjWHny 3CwQnEDpqGgRKb/R/F8Oy02HX58OslWlSQ7SUab0W2EopRoCoPVAj7bMtFCxUIn7xL dunmQiyr3NoFQDVk7xpHBBqito2P9tnK6+PwXj6U= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Yu Kuai , Tejun Heo , Christoph Hellwig , Jens Axboe , Sasha Levin Subject: [PATCH 6.1 536/885] blk-cgroup: synchronize pd_free_fn() from blkg_free_workfn() and blkcg_deactivate_policy() Date: Tue, 7 Mar 2023 17:57:50 +0100 Message-Id: <20230307170025.780340286@linuxfoundation.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230307170001.594919529@linuxfoundation.org> References: <20230307170001.594919529@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Yu Kuai [ Upstream commit f1c006f1c6850c14040f8337753a63119bba39b9 ] Currently parent pd can be freed before child pd: t1: remove cgroup C1 blkcg_destroy_blkgs blkg_destroy list_del_init(&blkg->q_node) // remove blkg from queue list percpu_ref_kill(&blkg->refcnt) blkg_release call_rcu t2: from t1 __blkg_release blkg_free schedule_work t4: deactivate policy blkcg_deactivate_policy pd_free_fn // parent of C1 is freed first t3: from t2 blkg_free_workfn pd_free_fn If policy(for example, ioc_timer_fn() from iocost) access parent pd from child pd after pd_offline_fn(), then UAF can be triggered. Fix the problem by delaying 'list_del_init(&blkg->q_node)' from blkg_destroy() to blkg_free_workfn(), and using a new disk level mutex to synchronize blkg_free_workfn() and blkcg_deactivate_policy(). Signed-off-by: Yu Kuai Acked-by: Tejun Heo Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/20230119110350.2287325-4-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/blk-cgroup.c | 35 +++++++++++++++++++++++++++++------ include/linux/blkdev.h | 1 + 2 files changed, 30 insertions(+), 6 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 8d1b7757f1e4f..f8b21bead6552 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -87,16 +87,32 @@ static void blkg_free_workfn(struct work_struct *work) { struct blkcg_gq *blkg = container_of(work, struct blkcg_gq, free_work); + struct request_queue *q = blkg->q; int i; + /* + * pd_free_fn() can also be called from blkcg_deactivate_policy(), + * in order to make sure pd_free_fn() is called in order, the deletion + * of the list blkg->q_node is delayed to here from blkg_destroy(), and + * blkcg_mutex is used to synchronize blkg_free_workfn() and + * blkcg_deactivate_policy(). + */ + if (q) + mutex_lock(&q->blkcg_mutex); + for (i = 0; i < BLKCG_MAX_POLS; i++) if (blkg->pd[i]) blkcg_policy[i]->pd_free_fn(blkg->pd[i]); if (blkg->parent) blkg_put(blkg->parent); - if (blkg->q) - blk_put_queue(blkg->q); + + if (q) { + list_del_init(&blkg->q_node); + mutex_unlock(&q->blkcg_mutex); + blk_put_queue(q); + } + free_percpu(blkg->iostat_cpu); percpu_ref_exit(&blkg->refcnt); kfree(blkg); @@ -425,9 +441,14 @@ static void blkg_destroy(struct blkcg_gq *blkg) lockdep_assert_held(&blkg->q->queue_lock); lockdep_assert_held(&blkcg->lock); - /* Something wrong if we are trying to remove same group twice */ - WARN_ON_ONCE(list_empty(&blkg->q_node)); - WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node)); + /* + * blkg stays on the queue list until blkg_free_workfn(), see details in + * blkg_free_workfn(), hence this function can be called from + * blkcg_destroy_blkgs() first and again from blkg_destroy_all() before + * blkg_free_workfn(). + */ + if (hlist_unhashed(&blkg->blkcg_node)) + return; for (i = 0; i < BLKCG_MAX_POLS; i++) { struct blkcg_policy *pol = blkcg_policy[i]; @@ -439,7 +460,6 @@ static void blkg_destroy(struct blkcg_gq *blkg) blkg->online = false; radix_tree_delete(&blkcg->blkg_tree, blkg->q->id); - list_del_init(&blkg->q_node); hlist_del_init_rcu(&blkg->blkcg_node); /* @@ -1226,6 +1246,7 @@ int blkcg_init_disk(struct gendisk *disk) int ret; INIT_LIST_HEAD(&q->blkg_list); + mutex_init(&q->blkcg_mutex); new_blkg = blkg_alloc(&blkcg_root, disk, GFP_KERNEL); if (!new_blkg) @@ -1463,6 +1484,7 @@ void blkcg_deactivate_policy(struct request_queue *q, if (queue_is_mq(q)) blk_mq_freeze_queue(q); + mutex_lock(&q->blkcg_mutex); spin_lock_irq(&q->queue_lock); __clear_bit(pol->plid, q->blkcg_pols); @@ -1481,6 +1503,7 @@ void blkcg_deactivate_policy(struct request_queue *q, } spin_unlock_irq(&q->queue_lock); + mutex_unlock(&q->blkcg_mutex); if (queue_is_mq(q)) blk_mq_unfreeze_queue(q); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 891f8cbcd0436..1680b6e1e5362 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -487,6 +487,7 @@ struct request_queue { DECLARE_BITMAP (blkcg_pols, BLKCG_MAX_POLS); struct blkcg_gq *root_blkg; struct list_head blkg_list; + struct mutex blkcg_mutex; #endif struct queue_limits limits; -- 2.39.2