linux-kernel - [PATCH AUTOSEL 4.18 012/126] lightnvm: pblk: fix race on sysfs line state

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Message-Id: <20181031230754.29029-12-sashal@kernel.org>
Date:   Wed, 31 Oct 2018 19:06:00 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Javier González <javier@...igon.com>,
        Javier González <javier@...xlabs.com>,
        Matias Bjørling <mb@...htnvm.io>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.18 012/126] lightnvm: pblk: fix race on sysfs line state

From: Javier González <javier@...igon.com>

[ Upstream commit 44cdbdc657b23f75736eca3e88b781f009104363 ]

pblk exposes a sysfs interface that represents its internal state. Part
of this state is the map bitmap for the current open line, which should
be protected by the line lock to avoid a race when freeing the line
metadata. Currently, it is not.

This patch makes sure that the line state is consistent and NULL
bitmap pointers are not dereferenced.

Signed-off-by: Javier González <javier@...xlabs.com>
Signed-off-by: Matias Bjørling <mb@...htnvm.io>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/lightnvm/pblk-core.c  | 5 +++--
 drivers/lightnvm/pblk-sysfs.c | 8 +++++++-
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
index ed9cc977c8b3..f6427e805150 100644
--- a/drivers/lightnvm/pblk-core.c
+++ b/drivers/lightnvm/pblk-core.c
@@ -1538,13 +1538,14 @@ struct pblk_line *pblk_line_replace_data(struct pblk *pblk)
 	struct pblk_line *cur, *new = NULL;
 	unsigned int left_seblks;
 
-	cur = l_mg->data_line;
 	new = l_mg->data_next;
 	if (!new)
 		goto out;
-	l_mg->data_line = new;
 
 	spin_lock(&l_mg->free_lock);
+	cur = l_mg->data_line;
+	l_mg->data_line = new;
+
 	pblk_line_setup_metadata(new, l_mg, &pblk->lm);
 	spin_unlock(&l_mg->free_lock);
 
diff --git a/drivers/lightnvm/pblk-sysfs.c b/drivers/lightnvm/pblk-sysfs.c
index 88a0a7c407aa..432f7d94d369 100644
--- a/drivers/lightnvm/pblk-sysfs.c
+++ b/drivers/lightnvm/pblk-sysfs.c
@@ -262,8 +262,14 @@ static ssize_t pblk_sysfs_lines(struct pblk *pblk, char *page)
 		sec_in_line = l_mg->data_line->sec_in_line;
 		meta_weight = bitmap_weight(&l_mg->meta_bitmap,
 							PBLK_DATA_LINES);
-		map_weight = bitmap_weight(l_mg->data_line->map_bitmap,
+
+		spin_lock(&l_mg->data_line->lock);
+		if (l_mg->data_line->map_bitmap)
+			map_weight = bitmap_weight(l_mg->data_line->map_bitmap,
 							lm->sec_per_line);
+		else
+			map_weight = 0;
+		spin_unlock(&l_mg->data_line->lock);
 	}
 	spin_unlock(&l_mg->free_lock);
 
-- 
2.17.1