netdev - [PATCH v2 net-next 1/3] ref_tracker: implement use-after-free detection

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Message-Id: <20220204224237.2932026-2-eric.dumazet@gmail.com>
Date:   Fri,  4 Feb 2022 14:42:35 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH v2 net-next 1/3] ref_tracker: implement use-after-free detection

From: Eric Dumazet <edumazet@...gle.com>

Whenever ref_tracker_dir_init() is called, mark the struct ref_tracker_dir
as dead.

Test the dead status from ref_tracker_alloc() and ref_tracker_free()

This should detect buggy dev_put()/dev_hold() happening too late
in netdevice dismantle process.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/linux/ref_tracker.h | 2 ++
 lib/ref_tracker.c           | 5 +++++
 2 files changed, 7 insertions(+)

diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
index 60f3453be23e6881725d383c55f93143fda1e7a2..a443abda937d86ff534225bf16b958a9da295a7d 100644
--- a/include/linux/ref_tracker.h
+++ b/include/linux/ref_tracker.h
@@ -13,6 +13,7 @@ struct ref_tracker_dir {
 	spinlock_t		lock;
 	unsigned int		quarantine_avail;
 	refcount_t		untracked;
+	bool			dead;
 	struct list_head	list; /* List of active trackers */
 	struct list_head	quarantine; /* List of dead trackers */
 #endif
@@ -26,6 +27,7 @@ static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
 	INIT_LIST_HEAD(&dir->quarantine);
 	spin_lock_init(&dir->lock);
 	dir->quarantine_avail = quarantine_count;
+	dir->dead = false;
 	refcount_set(&dir->untracked, 1);
 	stack_depot_init();
 }
diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
index a6789c0c626b0f68ad67c264cd19177a63fb82d2..32ff6bd497f8e464eeb51a3628cb24bded0547da 100644
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -20,6 +20,7 @@ void ref_tracker_dir_exit(struct ref_tracker_dir *dir)
 	unsigned long flags;
 	bool leak = false;
 
+	dir->dead = true;
 	spin_lock_irqsave(&dir->lock, flags);
 	list_for_each_entry_safe(tracker, n, &dir->quarantine, head) {
 		list_del(&tracker->head);
@@ -72,6 +73,8 @@ int ref_tracker_alloc(struct ref_tracker_dir *dir,
 	gfp_t gfp_mask = gfp;
 	unsigned long flags;
 
+	WARN_ON_ONCE(dir->dead);
+
 	if (gfp & __GFP_DIRECT_RECLAIM)
 		gfp_mask |= __GFP_NOFAIL;
 	*trackerp = tracker = kzalloc(sizeof(*tracker), gfp_mask);
@@ -100,6 +103,8 @@ int ref_tracker_free(struct ref_tracker_dir *dir,
 	unsigned int nr_entries;
 	unsigned long flags;
 
+	WARN_ON_ONCE(dir->dead);
+
 	if (!tracker) {
 		refcount_dec(&dir->untracked);
 		return -EEXIST;
-- 
2.35.0.263.gb82422642f-goog