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mm: fix possible deadlock in kmemleak

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There are some AA deadlock issues in kmemleak, similar to the situation
reported by Breno [1].  The deadlock path is as follows:

mem_pool_alloc()
  -> raw_spin_lock_irqsave(&kmemleak_lock, flags);
      -> pr_warn()
          -> netconsole subsystem
	     -> netpoll
	         -> __alloc_skb
		   -> __create_object
		     -> raw_spin_lock_irqsave(&kmemleak_lock, flags);

To solve this problem, switch to printk_safe mode before printing warning
message, this will redirect all printk()-s to a special per-CPU buffer,
which will be flushed later from a safe context (irq work), and this
deadlock problem can be avoided.  The proper API to use should be
printk_deferred_enter()/printk_deferred_exit() [2].  Another way is to
place the warn print after kmemleak is released.

Link: https://lkml.kernel.org/r/20250822073541.1886469-1-gubowen5@huawei.com
Link: https://lore.kernel.org/all/20250731-kmemleak_lock-v1-1-728fd470198f@debian.org/#t [1]
Link: https://lore.kernel.org/all/5ca375cd-4a20-4807-b897-68b289626550@redhat.com/ [2]
Signed-off-by: Gu Bowen <gubowen5@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Breno Leitao <leitao@debian.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Lu Jialin <lujialin4@huawei.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Gu Bowen
2025-08-22 15:35:41 +08:00
committed by Andrew Morton
parent 6659d02799
commit c873ccbb2f
1 changed files with 20 additions and 7 deletions
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27
mm/kmemleak.c
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@@ -437,9 +437,15 @@ static struct kmemleak_object *__lookup_object(unsigned long ptr, int alias,
else if (untagged_objp == untagged_ptr || alias)
return object;
else {
/*
* Printk deferring due to the kmemleak_lock held.
* This is done to avoid deadlock.
*/
printk_deferred_enter();
kmemleak_warn("Found object by alias at 0x%08lx\n",
ptr);
dump_object_info(object);
printk_deferred_exit();
break;
}
}
@@ -736,6 +742,11 @@ static int __link_object(struct kmemleak_object *object, unsigned long ptr,
else if (untagged_objp + parent->size <= untagged_ptr)
link = &parent->rb_node.rb_right;
else {
/*
* Printk deferring due to the kmemleak_lock held.
* This is done to avoid deadlock.
*/
printk_deferred_enter();
kmemleak_stop("Cannot insert 0x%lx into the object search tree (overlaps existing)\n",
ptr);
/*
@@ -743,6 +754,7 @@ static int __link_object(struct kmemleak_object *object, unsigned long ptr,
* be freed while the kmemleak_lock is held.
*/
dump_object_info(parent);
printk_deferred_exit();
return -EEXIST;
}
}
@@ -856,13 +868,8 @@ static void delete_object_part(unsigned long ptr, size_t size,
raw_spin_lock_irqsave(&kmemleak_lock, flags);
object = __find_and_remove_object(ptr, 1, objflags);
if (!object) {
#ifdef DEBUG
kmemleak_warn("Partially freeing unknown object at 0x%08lx (size %zu)\n",
ptr, size);
#endif
if (!object)
goto unlock;
}
/*
* Create one or two objects that may result from the memory block
@@ -882,8 +889,14 @@ static void delete_object_part(unsigned long ptr, size_t size,
unlock:
raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
if (object)
if (object) {
__delete_object(object);
} else {
#ifdef DEBUG
kmemleak_warn("Partially freeing unknown object at 0x%08lx (size %zu)\n",
ptr, size);
#endif
}
out:
if (object_l)