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authorWaiman Long <longman@redhat.com>2023-01-19 07:01:10 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-02-03 09:33:25 +0300
commit6061e740822530a4ef443548b19c4e0bc6342c7a (patch)
treed808393e8df943d0d95dbf5c3b29f76d0df15307 /mm/kmemleak.c
parent4cf1fe34fd18b752ae2403927277715d4444f331 (diff)
downloadlinux-6061e740822530a4ef443548b19c4e0bc6342c7a.tar.xz
mm/kmemleak: simplify kmemleak_cond_resched() usage
Patch series "mm/kmemleak: Simplify kmemleak_cond_resched() & fix UAF", v2. It was found that a KASAN use-after-free error was reported in the kmemleak_scan() function. After further examination, it is believe that even though a reference is taken from the current object, it does not prevent the object pointed to by the next pointer from going away after a cond_resched(). To fix that, additional flags are added to make sure that the current object won't be removed from the object_list during the duration of the cond_resched() to ensure the validity of the next pointer. While making the change, I also simplify the current usage of kmemleak_cond_resched() to make it easier to understand. This patch (of 2): The presence of a pinned argument and the 64k loop count make kmemleak_cond_resched() a bit more complex to read. The pinned argument is used only by first kmemleak_scan() loop. Simplify the usage of kmemleak_cond_resched() by removing the pinned argument and always do a get_object()/put_object() sequence. In addition, the 64k loop is removed by using need_resched() to decide if kmemleak_cond_resched() should be called. Link: https://lkml.kernel.org/r/20230119040111.350923-1-longman@redhat.com Link: https://lkml.kernel.org/r/20230119040111.350923-2-longman@redhat.com Signed-off-by: Waiman Long <longman@redhat.com> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Muchun Song <songmuchun@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/kmemleak.c')
-rw-r--r--mm/kmemleak.c48
1 files changed, 12 insertions, 36 deletions
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 55dc8b8b0616..69327b71fcf9 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1472,22 +1472,17 @@ static void scan_gray_list(void)
/*
* Conditionally call resched() in an object iteration loop while making sure
* that the given object won't go away without RCU read lock by performing a
- * get_object() if !pinned.
- *
- * Return: false if can't do a cond_resched() due to get_object() failure
- * true otherwise
+ * get_object() if necessaary.
*/
-static bool kmemleak_cond_resched(struct kmemleak_object *object, bool pinned)
+static void kmemleak_cond_resched(struct kmemleak_object *object)
{
- if (!pinned && !get_object(object))
- return false;
+ if (!get_object(object))
+ return; /* Try next object */
rcu_read_unlock();
cond_resched();
rcu_read_lock();
- if (!pinned)
- put_object(object);
- return true;
+ put_object(object);
}
/*
@@ -1501,15 +1496,12 @@ static void kmemleak_scan(void)
struct zone *zone;
int __maybe_unused i;
int new_leaks = 0;
- int loop_cnt = 0;
jiffies_last_scan = jiffies;
/* prepare the kmemleak_object's */
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list) {
- bool obj_pinned = false;
-
raw_spin_lock_irq(&object->lock);
#ifdef DEBUG
/*
@@ -1535,19 +1527,13 @@ static void kmemleak_scan(void)
/* reset the reference count (whiten the object) */
object->count = 0;
- if (color_gray(object) && get_object(object)) {
+ if (color_gray(object) && get_object(object))
list_add_tail(&object->gray_list, &gray_list);
- obj_pinned = true;
- }
raw_spin_unlock_irq(&object->lock);
- /*
- * Do a cond_resched() every 64k objects to avoid soft lockup.
- */
- if (!(++loop_cnt & 0xffff) &&
- !kmemleak_cond_resched(object, obj_pinned))
- loop_cnt--; /* Try again on next object */
+ if (need_resched())
+ kmemleak_cond_resched(object);
}
rcu_read_unlock();
@@ -1614,14 +1600,9 @@ static void kmemleak_scan(void)
* scan and color them gray until the next scan.
*/
rcu_read_lock();
- loop_cnt = 0;
list_for_each_entry_rcu(object, &object_list, object_list) {
- /*
- * Do a cond_resched() every 64k objects to avoid soft lockup.
- */
- if (!(++loop_cnt & 0xffff) &&
- !kmemleak_cond_resched(object, false))
- loop_cnt--; /* Try again on next object */
+ if (need_resched())
+ kmemleak_cond_resched(object);
/*
* This is racy but we can save the overhead of lock/unlock
@@ -1656,14 +1637,9 @@ static void kmemleak_scan(void)
* Scanning result reporting.
*/
rcu_read_lock();
- loop_cnt = 0;
list_for_each_entry_rcu(object, &object_list, object_list) {
- /*
- * Do a cond_resched() every 64k objects to avoid soft lockup.
- */
- if (!(++loop_cnt & 0xffff) &&
- !kmemleak_cond_resched(object, false))
- loop_cnt--; /* Try again on next object */
+ if (need_resched())
+ kmemleak_cond_resched(object);
/*
* This is racy but we can save the overhead of lock/unlock