linux-kernel - [PATCH] nvme: fix inconsistent RCU list manipulation in nvme_ns_add_to_ctrl

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Message-Id: <20250701071717.2619384-1-zhengqixing@huaweicloud.com>
Date: Tue,  1 Jul 2025 15:17:17 +0800
From: Zheng Qixing <zhengqixing@...weicloud.com>
To: kbusch@...nel.org,
	axboe@...nel.dk,
	hch@....de,
	sagi@...mberg.me
Cc: linux-nvme@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	yukuai3@...wei.com,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	houtao1@...wei.com,
	zhengqixing@...wei.com
Subject: [PATCH] nvme: fix inconsistent RCU list manipulation in nvme_ns_add_to_ctrl_list()

From: Zheng Qixing <zhengqixing@...wei.com>

When inserting a namespace into the controller's namespace list,
the function uses list_add_rcu() when the namespace is inserted
in the middle of the list, but falls back to a regular list_add()
when adding at the head of the list.

This inconsistency could lead to race conditions during concurrent
access, as users might observe a partially updated list. Fix this
by consistently using list_add_rcu() in both code paths to ensure
proper RCU protection throughout the entire function.

Fixes: be647e2c76b2 ("nvme: use srcu for iterating namespace list")
Signed-off-by: Zheng Qixing <zhengqixing@...wei.com>
---
 drivers/nvme/host/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index e533d791955d..475115edbbe9 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4077,7 +4077,7 @@ static void nvme_ns_add_to_ctrl_list(struct nvme_ns *ns)
 			return;
 		}
 	}
-	list_add(&ns->list, &ns->ctrl->namespaces);
+	list_add_rcu(&ns->list, &ns->ctrl->namespaces);
 }
 
 static void nvme_alloc_ns(struct nvme_ctrl *ctrl, struct nvme_ns_info *info)
-- 
2.39.2