111 lines
3.5 KiB
Diff
111 lines
3.5 KiB
Diff
From 8b190cfe2c3ec71bbb031dcf4eab072a4c83c289 Mon Sep 17 00:00:00 2001
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From: Gu Bowen <gubowen5@huawei.com>
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Date: Fri, 22 Aug 2025 15:35:41 +0800
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Subject: mm: fix possible deadlock in kmemleak
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There are some AA deadlock issues in kmemleak, similar to the situation
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reported by Breno [1]. The deadlock path is as follows:
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mem_pool_alloc()
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-> raw_spin_lock_irqsave(&kmemleak_lock, flags);
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-> pr_warn()
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-> netconsole subsystem
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-> netpoll
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-> __alloc_skb
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-> __create_object
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-> raw_spin_lock_irqsave(&kmemleak_lock, flags);
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To solve this problem, switch to printk_safe mode before printing warning
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message, this will redirect all printk()-s to a special per-CPU buffer,
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which will be flushed later from a safe context (irq work), and this
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deadlock problem can be avoided. The proper API to use should be
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printk_deferred_enter()/printk_deferred_exit() [2]. Another way is to
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place the warn print after kmemleak is released.
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Link: https://lkml.kernel.org/r/20250822073541.1886469-1-gubowen5@huawei.com
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Link: https://lore.kernel.org/all/20250731-kmemleak_lock-v1-1-728fd470198f@debian.org/#t [1]
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Link: https://lore.kernel.org/all/5ca375cd-4a20-4807-b897-68b289626550@redhat.com/ [2]
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Signed-off-by: Gu Bowen <gubowen5@huawei.com>
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Reviewed-by: Waiman Long <longman@redhat.com>
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Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
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Reviewed-by: Breno Leitao <leitao@debian.org>
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Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Cc: John Ogness <john.ogness@linutronix.de>
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Cc: Lu Jialin <lujialin4@huawei.com>
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Cc: Petr Mladek <pmladek@suse.com>
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Cc: <stable@vger.kernel.org>
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Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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---
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mm/kmemleak.c | 27 ++++++++++++++++++++-------
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1 file changed, 20 insertions(+), 7 deletions(-)
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--- a/mm/kmemleak.c
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+++ b/mm/kmemleak.c
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@@ -437,9 +437,15 @@ static struct kmemleak_object *__lookup_
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else if (untagged_objp == untagged_ptr || alias)
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return object;
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else {
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+ /*
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+ * Printk deferring due to the kmemleak_lock held.
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+ * This is done to avoid deadlock.
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+ */
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+ printk_deferred_enter();
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kmemleak_warn("Found object by alias at 0x%08lx\n",
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ptr);
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dump_object_info(object);
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+ printk_deferred_exit();
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break;
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}
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}
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@@ -736,6 +742,11 @@ static int __link_object(struct kmemleak
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else if (untagged_objp + parent->size <= untagged_ptr)
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link = &parent->rb_node.rb_right;
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else {
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+ /*
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+ * Printk deferring due to the kmemleak_lock held.
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+ * This is done to avoid deadlock.
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+ */
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+ printk_deferred_enter();
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kmemleak_stop("Cannot insert 0x%lx into the object search tree (overlaps existing)\n",
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ptr);
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/*
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@@ -743,6 +754,7 @@ static int __link_object(struct kmemleak
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* be freed while the kmemleak_lock is held.
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*/
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dump_object_info(parent);
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+ printk_deferred_exit();
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return -EEXIST;
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}
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}
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@@ -856,13 +868,8 @@ static void delete_object_part(unsigned
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raw_spin_lock_irqsave(&kmemleak_lock, flags);
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object = __find_and_remove_object(ptr, 1, objflags);
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- if (!object) {
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-#ifdef DEBUG
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- kmemleak_warn("Partially freeing unknown object at 0x%08lx (size %zu)\n",
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- ptr, size);
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-#endif
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+ if (!object)
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goto unlock;
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- }
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/*
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* Create one or two objects that may result from the memory block
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@@ -882,8 +889,14 @@ static void delete_object_part(unsigned
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unlock:
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raw_spin_unlock_irqrestore(&kmemleak_lock, flags);
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- if (object)
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+ if (object) {
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__delete_object(object);
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+ } else {
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+#ifdef DEBUG
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+ kmemleak_warn("Partially freeing unknown object at 0x%08lx (size %zu)\n",
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+ ptr, size);
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+#endif
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+ }
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out:
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if (object_l)
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