linux-kernel - [PATCH v4 2/8] blk-cgroup: Fix class @block

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Message-Id: <20241218-class_fix-v4-2-3c40f098356b@quicinc.com>
Date: Wed, 18 Dec 2024 08:01:32 +0800
From: Zijun Hu <zijun_hu@...oud.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 "Rafael J. Wysocki" <rafael@...nel.org>, Tejun Heo <tj@...nel.org>, 
 Josef Bacik <josef@...icpanda.com>, Jens Axboe <axboe@...nel.dk>, 
 Boris Burkov <boris@....io>, Davidlohr Bueso <dave@...olabs.net>, 
 Jonathan Cameron <jonathan.cameron@...wei.com>, 
 Dave Jiang <dave.jiang@...el.com>, 
 Alison Schofield <alison.schofield@...el.com>, 
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, 
 Dan Williams <dan.j.williams@...el.com>
Cc: Zijun Hu <zijun_hu@...oud.com>, linux-kernel@...r.kernel.org, 
 cgroups@...r.kernel.org, linux-block@...r.kernel.org, 
 linux-cxl@...r.kernel.org, Zijun Hu <quic_zijuhu@...cinc.com>, 
 Michal Koutný <mkoutny@...e.com>, stable@...r.kernel.org
Subject: [PATCH v4 2/8] blk-cgroup: Fix class @block_class's subsystem
 refcount leakage

From: Zijun Hu <quic_zijuhu@...cinc.com>

blkcg_fill_root_iostats() iterates over @block_class's devices by
class_dev_iter_(init|next)(), but does not end iterating with
class_dev_iter_exit(), so causes the class's subsystem refcount leakage.

Fix by ending the iterating with class_dev_iter_exit().

Fixes: ef45fe470e1e ("blk-cgroup: show global disk stats in root cgroup io.stat")
Reviewed-by: Michal Koutný <mkoutny@...e.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: stable@...r.kernel.org
Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
---
 block/blk-cgroup.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index e68c725cf8d975f53703ecf6e6c50594076204c8..fb9858efdfe9443704cb9a239def0e08addf2518 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1138,6 +1138,7 @@ static void blkcg_fill_root_iostats(void)
 		blkg_iostat_set(&blkg->iostat.cur, &tmp);
 		u64_stats_update_end_irqrestore(&blkg->iostat.sync, flags);
 	}
+	class_dev_iter_exit(&iter);
 }

 static void blkcg_print_one_stat(struct blkcg_gq *blkg, struct seq_file *s)

-- 
2.34.1