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 BA0652206B8; Mon, 18 Aug 2025 13:41:56 +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=1755524516; cv=none; b=AS6JkkjJuHiYdPprs2xA7dpjPbKBKU7e9VMY4mzkPPMysF4cv1JIhHiSnU43YHx4n8VpJdB9v8szL7gQRdnruyQfMwdbU4WD7k/+1sVK+e8HpTLDdX9OLzFpFyGvouOI9CpedTebTiCWQtrSNWqn6fX8rzhY3KyFrGOZoOkrqD0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755524516; c=relaxed/simple; bh=nSDOXL8ly0lsCRpCrUIAd+gAUdPyUVhnTxmzCMcCy6E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RsZpufN5Zr9/KGdvKy82Gey5rbvtmWRWAy/M13A6cfh6I7Bmn5igJAxtsu7uuYwxiFHtIMgzt3RJhDlY9AONrWUDYkE5CM1h7JE7PpVZrkhl/VW9bkvIQlwG0/6PebFNbs2NEtUreYC0L2W9VXW/OIpPSHIZ0JO/B1cSWHrVK1U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=W/WtZcyi; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="W/WtZcyi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 85BFAC113D0; Mon, 18 Aug 2025 13:41:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1755524516; bh=nSDOXL8ly0lsCRpCrUIAd+gAUdPyUVhnTxmzCMcCy6E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=W/WtZcyiSQhZUvZj0mXV7/00Sx3d6rc/W5nQcNnUDeQ0CCUiPk2qDgbnvHzT43qxZ jsU2N4jPk5cAe+5qXEdBFwYFgGejYN0lWwfXtijV+j2tcRt2YkOqzoxiax27Raycpe uKhMSSNYZrux2HzxKtwdPltnS+7RReiBn8EkGKzc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Breno Leitao , Jakub Kicinski , Catalin Marinas , Andrew Morton Subject: [PATCH 6.15 495/515] mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock Date: Mon, 18 Aug 2025 14:48:01 +0200 Message-ID: <20250818124517.501575473@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250818124458.334548733@linuxfoundation.org> References: <20250818124458.334548733@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Breno Leitao commit 47b0f6d8f0d2be4d311a49e13d2fd5f152f492b2 upstream. When netpoll is enabled, calling pr_warn_once() while holding kmemleak_lock in mem_pool_alloc() can cause a deadlock due to lock inversion with the netconsole subsystem. This occurs because pr_warn_once() may trigger netpoll, which eventually leads to __alloc_skb() and back into kmemleak code, attempting to reacquire kmemleak_lock. This is the path for the deadlock. mem_pool_alloc() -> raw_spin_lock_irqsave(&kmemleak_lock, flags); -> pr_warn_once() -> netconsole subsystem -> netpoll -> __alloc_skb -> __create_object -> raw_spin_lock_irqsave(&kmemleak_lock, flags); Fix this by setting a flag and issuing the pr_warn_once() after kmemleak_lock is released. Link: https://lkml.kernel.org/r/20250731-kmemleak_lock-v1-1-728fd470198f@debian.org Fixes: c5665868183f ("mm: kmemleak: use the memory pool for early allocations") Signed-off-by: Breno Leitao Reported-by: Jakub Kicinski Acked-by: Catalin Marinas Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/kmemleak.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -475,6 +475,7 @@ static struct kmemleak_object *mem_pool_ { unsigned long flags; struct kmemleak_object *object; + bool warn = false; /* try the slab allocator first */ if (object_cache) { @@ -493,8 +494,10 @@ static struct kmemleak_object *mem_pool_ else if (mem_pool_free_count) object = &mem_pool[--mem_pool_free_count]; else - pr_warn_once("Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE\n"); + warn = true; raw_spin_unlock_irqrestore(&kmemleak_lock, flags); + if (warn) + pr_warn_once("Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE\n"); return object; }