From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: linux-kernel@vger.kernel.org
Cc: tglx@linutronix.de, Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
linux-mm@kvack.org, Shaohua Li <shli@kernel.org>,
linux-raid@vger.kernel.org,
Anna-Maria Gleixner <anna-maria@linutronix.de>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: [PATCH 1/8] bdi: use refcount_t for reference counting instead atomic_t
Date: Wed, 9 May 2018 21:36:38 +0200 [thread overview]
Message-ID: <20180509193645.830-2-bigeasy@linutronix.de> (raw)
In-Reply-To: <20180509193645.830-1-bigeasy@linutronix.de>
refcount_t type and corresponding API should be used instead of atomic_t when
the variable is used as a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free situations.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
include/linux/backing-dev-defs.h | 3 ++-
include/linux/backing-dev.h | 4 ++--
mm/backing-dev.c | 12 ++++++------
3 files changed, 10 insertions(+), 9 deletions(-)
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index 0bd432a4d7bd..81c75934ca5b 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -12,6 +12,7 @@
#include <linux/timer.h>
#include <linux/workqueue.h>
#include <linux/kref.h>
+#include <linux/refcount.h>
struct page;
struct device;
@@ -76,7 +77,7 @@ enum wb_reason {
*/
struct bdi_writeback_congested {
unsigned long state; /* WB_[a]sync_congested flags */
- atomic_t refcnt; /* nr of attached wb's and blkg */
+ refcount_t refcnt; /* nr of attached wb's and blkg */
#ifdef CONFIG_CGROUP_WRITEBACK
struct backing_dev_info *__bdi; /* the associated bdi, set to NULL
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 72ca0f3d39f3..c28a47cbe355 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -404,13 +404,13 @@ static inline bool inode_cgwb_enabled(struct inode *inode)
static inline struct bdi_writeback_congested *
wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
{
- atomic_inc(&bdi->wb_congested->refcnt);
+ refcount_inc(&bdi->wb_congested->refcnt);
return bdi->wb_congested;
}
static inline void wb_congested_put(struct bdi_writeback_congested *congested)
{
- if (atomic_dec_and_test(&congested->refcnt))
+ if (refcount_dec_and_test(&congested->refcnt))
kfree(congested);
}
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 7441bd93b732..7984a872073e 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -450,10 +450,10 @@ 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);
@@ -463,13 +463,13 @@ 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;
@@ -486,7 +486,7 @@ 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;
}
@@ -794,7 +794,7 @@ 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) {
--
2.17.0
next prev parent reply other threads:[~2018-05-09 19:38 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-09 19:36 [PATCH v2 0/8] Introduce refcount_dec_and_lock_irqsave() Sebastian Andrzej Siewior
2018-05-09 19:36 ` Sebastian Andrzej Siewior [this message]
2018-05-09 19:36 ` [PATCH 2/8] userns: use refcount_t for reference counting instead atomic_t Sebastian Andrzej Siewior
2018-05-09 19:36 ` [PATCH 3/8] md: raid5: " Sebastian Andrzej Siewior
2018-05-23 12:36 ` Peter Zijlstra
2018-05-23 12:50 ` Sebastian Andrzej Siewior
2018-05-23 12:55 ` Peter Zijlstra
2018-05-23 13:21 ` Matthew Wilcox
2018-05-23 17:49 ` Peter Zijlstra
2018-05-23 19:22 ` Shaohua Li
2018-05-24 7:14 ` Peter Zijlstra
2018-05-09 19:36 ` [PATCH 4/8] locking/refcount: implement refcount_dec_and_lock_irqsave() Sebastian Andrzej Siewior
2018-05-09 19:36 ` [PATCH 5/8] bdi: Use irqsave variant of refcount_dec_and_lock() Sebastian Andrzej Siewior
2018-05-09 19:36 ` [PATCH 6/8] userns: " Sebastian Andrzej Siewior
2018-05-09 19:36 ` [PATCH 7/8] md: raid5: " Sebastian Andrzej Siewior
2018-05-09 19:36 ` [PATCH 8/8] md: raid5: Do not disable irq on release_inactive_stripe_list() call Sebastian Andrzej Siewior
2018-05-23 13:01 ` [PATCH v2 0/8] Introduce refcount_dec_and_lock_irqsave() Peter Zijlstra
2018-05-23 13:09 ` Sebastian Andrzej Siewior
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