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mm/kmemleak: fix UAF bug in kmemleak_scan()

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Commit 6edda04ccc ("mm/kmemleak: prevent soft lockup in first object
iteration loop of kmemleak_scan()") fixes soft lockup problem in
kmemleak_scan() by periodically doing a cond_resched().  It does take a
reference of the current object before doing it.  Unfortunately, if the
object has been deleted from the object_list, the next object pointed to
by its next pointer may no longer be valid after coming back from
cond_resched().  This can result in use-after-free and other nasty
problem.

Fix this problem by adding a del_state flag into kmemleak_object structure
to synchronize the object deletion process between kmemleak_cond_resched()
and __remove_object() to make sure that the object remained in the
object_list in the duration of the cond_resched() call.

Link: https://lkml.kernel.org/r/20230119040111.350923-3-longman@redhat.com
Fixes: 6edda04ccc ("mm/kmemleak: prevent soft lockup in first object iteration loop of kmemleak_scan()")
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>
This commit is contained in:
Waiman Long 2023-01-18 23:01:11 -05:00 committed by Andrew Morton
parent 6061e74082
commit 782e417953
1 changed files with 29 additions and 6 deletions
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35
mm/kmemleak.c
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@ -13,11 +13,12 @@
*
* The following locks and mutexes are used by kmemleak:
*
* - kmemleak_lock (raw_spinlock_t): protects the object_list modifications and
* accesses to the object_tree_root (or object_phys_tree_root). The
* object_list is the main list holding the metadata (struct kmemleak_object)
* for the allocated memory blocks. The object_tree_root and object_phys_tree_root
* are red black trees used to look-up metadata based on a pointer to the
* - kmemleak_lock (raw_spinlock_t): protects the object_list as well as
* del_state modifications and accesses to the object_tree_root (or
* object_phys_tree_root). The object_list is the main list holding the
* metadata (struct kmemleak_object) for the allocated memory blocks.
* The object_tree_root and object_phys_tree_root are red
* black trees used to look-up metadata based on a pointer to the
* corresponding memory block. The object_phys_tree_root is for objects
* allocated with physical address. The kmemleak_object structures are
* added to the object_list and object_tree_root (or object_phys_tree_root)
@ -148,6 +149,7 @@ struct kmemleak_object {
struct rcu_head rcu; /* object_list lockless traversal */
/* object usage count; object freed when use_count == 0 */
atomic_t use_count;
unsigned int del_state; /* deletion state */
unsigned long pointer;
size_t size;
/* pass surplus references to this pointer */
@ -177,6 +179,11 @@ struct kmemleak_object {
/* flag set for object allocated with physical address */
#define OBJECT_PHYS (1 << 4)
/* set when __remove_object() called */
#define DELSTATE_REMOVED (1 << 0)
/* set to temporarily prevent deletion from object_list */
#define DELSTATE_NO_DELETE (1 << 1)
#define HEX_PREFIX " "
/* number of bytes to print per line; must be 16 or 32 */
#define HEX_ROW_SIZE 16
@ -571,7 +578,9 @@ static void __remove_object(struct kmemleak_object *object)
rb_erase(&object->rb_node, object->flags & OBJECT_PHYS ?
&object_phys_tree_root :
&object_tree_root);
list_del_rcu(&object->object_list);
if (!(object->del_state & DELSTATE_NO_DELETE))
list_del_rcu(&object->object_list);
object->del_state |= DELSTATE_REMOVED;
}
/*
@ -643,6 +652,7 @@ static void __create_object(unsigned long ptr, size_t size,
object->count = 0; /* white color initially */
object->jiffies = jiffies;
object->checksum = 0;
object->del_state = 0;
/* task information */
if (in_hardirq()) {
@ -1479,9 +1489,22 @@ static void kmemleak_cond_resched(struct kmemleak_object *object)
if (!get_object(object))
return; /* Try next object */
raw_spin_lock_irq(&kmemleak_lock);
if (object->del_state & DELSTATE_REMOVED)
goto unlock_put; /* Object removed */
object->del_state |= DELSTATE_NO_DELETE;
raw_spin_unlock_irq(&kmemleak_lock);
rcu_read_unlock();
cond_resched();
rcu_read_lock();
raw_spin_lock_irq(&kmemleak_lock);
if (object->del_state & DELSTATE_REMOVED)
list_del_rcu(&object->object_list);
object->del_state &= ~DELSTATE_NO_DELETE;
unlock_put:
raw_spin_unlock_irq(&kmemleak_lock);
put_object(object);
}