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 0BD2814A4DF; Thu, 23 May 2024 13:16:00 +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=1716470160; cv=none; b=E0nOObZYwiyiSDQAvcBGYKyb7iKbxsNS2ilCMw5fVXKVivBlagh+LgC+2NuLd5BUP0ZUlwoiB4EK/MBcVVpnxVmtrOmRj4SuScbKvopjMBRr/eTx6xFrc9rYg1Tag+ovyFrmHV6IyJHytYqllV0uw1A/83JxeD5oJshetpw6e8k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716470160; c=relaxed/simple; bh=pzMwzv6sFCf/5Ejvtn6ejTxGWgM9yUjsIfnF8r+RJcA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sJqaYGVipx9u8Q1X8Or+zfwu3a35S+Ql7kjnqdHFgHCzJYU54F7vq//5C4n6KTa5dHyJpS2MU3r+8wUuoLD3glbuBqOoiVGwEDfa5ExJxwfOvYtLM9ltQrXcXEnQ5s5r6RN4p7WQHfMr1uAiDZJbdOP8wj8B3OSRooRi3dlRfpw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xt/NVljr; 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="xt/NVljr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8781BC2BD10; Thu, 23 May 2024 13:15:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1716470159; bh=pzMwzv6sFCf/5Ejvtn6ejTxGWgM9yUjsIfnF8r+RJcA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xt/NVljrDYlvdp5Llmaj1a7gicCNXB4mIjkGuVaiSi1I22OLVlp+R2hGuDz/pzd1U YuisREfWoOFZGB71Vq+vsb2abQNRblX4f+8+RI04mQ6zkEV67mCL69Qya7Yh/bI8ch IqKGVMNUBdGXRyoGRyu/oZ8O09ixPd42bXlzel9k= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Liuye , Douglas Anderson , Daniel Thompson Subject: [PATCH 5.4 15/16] serial: kgdboc: Fix NMI-safety problems from keyboard reset code Date: Thu, 23 May 2024 15:12:48 +0200 Message-ID: <20240523130326.320872856@linuxfoundation.org> X-Mailer: git-send-email 2.45.1 In-Reply-To: <20240523130325.743454852@linuxfoundation.org> References: <20240523130325.743454852@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Thompson commit b2aba15ad6f908d1a620fd97f6af5620c3639742 upstream. Currently, when kdb is compiled with keyboard support, then we will use schedule_work() to provoke reset of the keyboard status. Unfortunately schedule_work() gets called from the kgdboc post-debug-exception handler. That risks deadlock since schedule_work() is not NMI-safe and, even on platforms where the NMI is not directly used for debugging, the debug trap can have NMI-like behaviour depending on where breakpoints are placed. Fix this by using the irq work system, which is NMI-safe, to defer the call to schedule_work() to a point when it is safe to call. Reported-by: Liuye Closes: https://lore.kernel.org/all/20240228025602.3087748-1-liu.yeC@h3c.com/ Cc: stable@vger.kernel.org Reviewed-by: Douglas Anderson Acked-by: Greg Kroah-Hartman Link: https://lore.kernel.org/r/20240424-kgdboc_fix_schedule_work-v2-1-50f5a490aec5@linaro.org Signed-off-by: Daniel Thompson Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/kgdboc.c | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) --- a/drivers/tty/serial/kgdboc.c +++ b/drivers/tty/serial/kgdboc.c @@ -19,6 +19,7 @@ #include #include #include +#include #include #include @@ -42,6 +43,25 @@ static int kgdb_tty_line; static struct platform_device *kgdboc_pdev; +/* + * When we leave the debug trap handler we need to reset the keyboard status + * (since the original keyboard state gets partially clobbered by kdb use of + * the keyboard). + * + * The path to deliver the reset is somewhat circuitous. + * + * To deliver the reset we register an input handler, reset the keyboard and + * then deregister the input handler. However, to get this done right, we do + * have to carefully manage the calling context because we can only register + * input handlers from task context. + * + * In particular we need to trigger the action from the debug trap handler with + * all its NMI and/or NMI-like oddities. To solve this the kgdboc trap exit code + * (the "post_exception" callback) uses irq_work_queue(), which is NMI-safe, to + * schedule a callback from a hardirq context. From there we have to defer the + * work again, this time using schedule_work(), to get a callback using the + * system workqueue, which runs in task context. + */ #ifdef CONFIG_KDB_KEYBOARD static int kgdboc_reset_connect(struct input_handler *handler, struct input_dev *dev, @@ -93,10 +113,17 @@ static void kgdboc_restore_input_helper( static DECLARE_WORK(kgdboc_restore_input_work, kgdboc_restore_input_helper); +static void kgdboc_queue_restore_input_helper(struct irq_work *unused) +{ + schedule_work(&kgdboc_restore_input_work); +} + +static DEFINE_IRQ_WORK(kgdboc_restore_input_irq_work, kgdboc_queue_restore_input_helper); + static void kgdboc_restore_input(void) { if (likely(system_state == SYSTEM_RUNNING)) - schedule_work(&kgdboc_restore_input_work); + irq_work_queue(&kgdboc_restore_input_irq_work); } static int kgdboc_register_kbd(char **cptr) @@ -127,6 +154,7 @@ static void kgdboc_unregister_kbd(void) i--; } } + irq_work_sync(&kgdboc_restore_input_irq_work); flush_work(&kgdboc_restore_input_work); } #else /* ! CONFIG_KDB_KEYBOARD */