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

[Sasha Levin]

From: Javier González <jav...@javigon.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 <jav...@cnexlabs.com>
Signed-off-by: Matias Bjørling <m...@lightnvm.io>
Signed-off-by: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Sasha Levin <sas...@kernel.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