bdi: use refcount_t for reference counting instead atomic_t
refcount_t type and corresponding API should be used instead of atomic_t
when the variable is used as a reference counter. This permits avoiding
accidental refcounter overflows that might lead to use-after-free
situations.
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Suggested-by: Peter Zijlstra <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 2e5d3df..55a233d 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -438,10 +438,10 @@ wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
if (new_congested) {
/* !found and storage for new one already allocated, insert */
congested = new_congested;
- new_congested = NULL;
rb_link_node(&congested->rb_node, parent, node);
rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree);
- goto found;
+ spin_unlock_irqrestore(&cgwb_lock, flags);
+ return congested;
}
spin_unlock_irqrestore(&cgwb_lock, flags);
@@ -451,13 +451,13 @@ wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
if (!new_congested)
return NULL;
- atomic_set(&new_congested->refcnt, 0);
+ refcount_set(&new_congested->refcnt, 1);
new_congested->__bdi = bdi;
new_congested->blkcg_id = blkcg_id;
goto retry;
found:
- atomic_inc(&congested->refcnt);
+ refcount_inc(&congested->refcnt);
spin_unlock_irqrestore(&cgwb_lock, flags);
kfree(new_congested);
return congested;
@@ -474,7 +474,7 @@ void wb_congested_put(struct bdi_writeback_congested *congested)
unsigned long flags;
local_irq_save(flags);
- if (!atomic_dec_and_lock(&congested->refcnt, &cgwb_lock)) {
+ if (!refcount_dec_and_lock(&congested->refcnt, &cgwb_lock)) {
local_irq_restore(flags);
return;
}
@@ -804,7 +804,7 @@ static int cgwb_bdi_init(struct backing_dev_info *bdi)
if (!bdi->wb_congested)
return -ENOMEM;
- atomic_set(&bdi->wb_congested->refcnt, 1);
+ refcount_set(&bdi->wb_congested->refcnt, 1);
err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
if (err) {
