lightnvm: pblk: fix race on sysfs line state

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@cnexlabs.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 10 insertions, 3 deletions

diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
index 4045a9b1ee74..6944aac43b01 100644
--- a/drivers/lightnvm/pblk-core.c
+++ b/drivers/lightnvm/pblk-core.c
@@ -1611,13 +1611,14 @@ 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 cba83ac43e62..2d2818155aa8 100644
--- a/drivers/lightnvm/pblk-sysfs.c
+++ b/drivers/lightnvm/pblk-sysfs.c
@@ -263,8 +263,14 @@ 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);