diff options
| author |   Gu Bowen <gubowen5@huawei.com> | 2025-08-22 15:35:41 +0800 |
|---|---|---|
| committer |   Andrew Morton <akpm@linux-foundation.org> | 2025-09-01 17:11:37 -0700 |
| commit | c873ccbb2f8db46ad9b4a989ea924b6d8f19abf1 (patch) | |
| tree | f2688fca5882394acc6416ffe74486de63b59996 | |
| parent | x86/mm/64: define ARCH_PAGE_TABLE_SYNC_MASK and arch_sync_kernel_mappings() (diff) | |
| download | wireguard-linux-c873ccbb2f8db46ad9b4a989ea924b6d8f19abf1.tar.xz wireguard-linux-c873ccbb2f8db46ad9b4a989ea924b6d8f19abf1.zip | |
mm: fix possible deadlock in kmemleak
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>
| -rw-r--r-- | mm/kmemleak.c | 27 |
1 files changed, 20 insertions, 7 deletions
diff --git a/mm/kmemleak.c b/mm/kmemleak.c index 84265983f239..1ac56ceb29b6 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -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) |