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>

diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
index 4045a9b1ee74d8a2331ca12d2d6d71cb5d11ed36..6944aac43b015de6625ca08d0b50a8514f13768d 100644 (file)
--- 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 cba83ac43e62de5555b551589f9f468b8121c1c8..2d2818155aa8a18e42d18de657af08b136659820 100644 (file)
--- 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);