From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A4F493234; Sat, 23 Aug 2025 00:48:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755910116; cv=none; b=cfczzZIcphTWUsI7eybopa261gUAfZcZ0ypty0hi0QdE9J++n/6JyH9lcePrhkA0LQz56Wcs+TXQP8X5xS1Gp4luVuH9B7yl2lxuXTabhcRcq+aRxp69KA1Mt59GZOwPr74vbBairOEyqCVUTasLYxBa7wXEgdJpyIu9zt+cAUY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755910116; c=relaxed/simple; bh=zrqluCsZft0A80ykme0GAbiSiNy7CX/v0bduFveBWuE=; h=Date:To:From:Subject:Message-Id; b=IJfN3/QZxjx9aVQii+fWmY3zMETN0ooZjZZxAv7w5igBCTDUi+RVLUKzS/6oaRfCIYfWaCCnmQG35u4Bm2QZBnAw5mwf7eUVnsRMtFOUlO/joyrghoyiRLGx2zw66P+sPNmMrDELJr1YG64JS6jo+7tfor0sKZyiJ7jCLZG4F2c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=UZLCT4GO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="UZLCT4GO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EB3E7C4CEED; Sat, 23 Aug 2025 00:48:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1755910114; bh=zrqluCsZft0A80ykme0GAbiSiNy7CX/v0bduFveBWuE=; h=Date:To:From:Subject:From; b=UZLCT4GO7nwp6z1xjcjm2tupMSh9MjMoTEm7QutlDAXohnfOoUv6a4rgYcWYjnDIX 3DHej53bt2cQRIZKKqrWt8dX+IdQQ7rw62krESm0nZ9EgbWSfedNHIPSued96gnnWF le7zOrOPLV0ShLsg7X192Tt1L/HkxNo9wiWt+NqI= Date: Fri, 22 Aug 2025 17:48:33 -0700 To: mm-commits@vger.kernel.org,stable@vger.kernel.org,pmladek@suse.com,lujialin4@huawei.com,leitao@debian.org,john.ogness@linutronix.de,gregkh@linuxfoundation.org,catalin.marinas@arm.com,gubowen5@huawei.com,akpm@linux-foundation.org From: Andrew Morton Subject: + mm-fix-possible-deadlock-in-kmemleak.patch added to mm-hotfixes-unstable branch Message-Id: <20250823004833.EB3E7C4CEED@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: mm: gix possible deadlock in kmemleak has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-fix-possible-deadlock-in-kmemleak.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-fix-possible-deadlock-in-kmemleak.patch This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Gu Bowen Subject: mm: gix possible deadlock in kmemleak Date: Fri, 22 Aug 2025 15:35:41 +0800 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 Cc: Breno Leitao Cc: Catalin Marinas Cc: Greg Kroah-Hartman Cc: John Ogness Cc: Lu Jialin Cc: Petr Mladek Cc: Signed-off-by: Andrew Morton --- mm/kmemleak.c | 27 ++++++++++++++++++++------- 1 file changed, 20 insertions(+), 7 deletions(-) --- a/mm/kmemleak.c~mm-fix-possible-deadlock-in-kmemleak +++ a/mm/kmemleak.c @@ -437,9 +437,15 @@ static struct kmemleak_object *__lookup_ 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 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 * 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 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 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) _ Patches currently in -mm which might be from gubowen5@huawei.com are mm-fix-possible-deadlock-in-kmemleak.patch