From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (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 0480472 for ; Thu, 26 Aug 2021 10:01:08 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id AAADF60FDA; Thu, 26 Aug 2021 10:01:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1629972068; bh=aBkNesMqvbH7PzlPklFkGTRo82VXoOZrWukyGg5zmgk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=0TZIGZ6ilntOAA5Vy+88jsU2oXA4xJa+hAZtzNtj08DKsb39Yj8kyw/ZXdSdCUBWK 5YuBrPb+Q8mXpsIfk/6G+BuvewMhUVIHhLvKmSjO3r/6e8jd0zD8n46+Lrd1zV+5qw nCowxPqAHqV5Npi85sjUfToxptVMdt1mWTa3HdaA= Date: Thu, 26 Aug 2021 12:01:03 +0200 From: Greg Kroah-Hartman To: Woody Lin Cc: Todd Kjos , Arve =?iso-8859-1?B?SGr4bm5lduVn?= , Martijn Coenen , Joel Fernandes , Christian Brauner , Hridya Valsaraju , Suren Baghdasaryan , linux-kernel@vger.kernel.org, linux-staging@lists.linux.dev Subject: Re: [PATCH] ANDROID: staging: add userpanic-dev driver Message-ID: References: <20210826092854.58694-1-woodylin@google.com> Precedence: bulk X-Mailing-List: linux-staging@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210826092854.58694-1-woodylin@google.com> On Thu, Aug 26, 2021 at 05:28:54PM +0800, Woody Lin wrote: > Add char device driver 'userpanic-dev' that exposes an interface to > userspace processes to request a system panic with customized panic > message. Some comments on the code now: > obj-$(CONFIG_ASHMEM) += ashmem.o > +obj-$(CONFIG_USERPANIC_CHARDEV) += userpanic-dev.o Why CHARDEV? > diff --git a/drivers/staging/android/userpanic-dev.c b/drivers/staging/android/userpanic-dev.c > new file mode 100644 > index 000000000000..b9a0f0c01826 > --- /dev/null > +++ b/drivers/staging/android/userpanic-dev.c > @@ -0,0 +1,110 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* userpanic-dev.c > + * > + * User-panic Device Interface > + * > + * Copyright 2021 Google LLC > + */ > + > +#define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__ Why is this needed? > + > +#include > +#include > +#include > +#include > + > +struct userpanic_crash_info { > + void __user *title_uaddr; > + void __user *msg_uaddr; > +}; If this is a user/kernel api, it can not be burried in a .c file, otherwise it will be wrong over time. And this is NOT how to handle user/kernel pointers at all, please fix. > + > +#define CRASH_INFO (_IOW('U', 179, struct userpanic_crash_info)) Why does this have to be an ioctl at all? Why do you have to have a char device for this? > + > +static int do_userpanic(const char *title, const char *msg) > +{ > + const size_t msgbuf_sz = PAGE_SIZE; > + char *msgbuf; > + > + msgbuf = kmalloc(msgbuf_sz, GFP_KERNEL); > + if (!msgbuf) > + return -ENOMEM; > + > + pr_emerg("User process '%.*s' %d requesting kernel panic\n", > + sizeof(current->comm), current->comm, current->pid); You have a pointer to a struct device, always use it for this and all other messages, it should be dev_*(), right? > + if (msg) > + pr_emerg(" with message: %s\n", msg); Multi line messages? Why? > + > + /* Request panic with customized panic title. */ > + snprintf(msgbuf, msgbuf_sz, "U: %s: %s", current->comm, title); > + panic(msgbuf); > + kfree(msgbuf); Nice, you cleaned up after panicing? Why? > + return -EFAULT; > +} > + > +static long userpanic_device_ioctl(struct file *file, u_int cmd, u_long arg) > +{ > + struct userpanic_crash_info crash_info; > + char *title; > + char *msg = NULL; > + int ret; > + > + switch (cmd) { > + case CRASH_INFO: > + if (copy_from_user(&crash_info, (void __user *)arg, sizeof(crash_info))) > + return -EFAULT; > + > + if (!crash_info.title_uaddr) > + return -EINVAL; > + > + title = strndup_user(crash_info.title_uaddr, PAGE_SIZE); What if the string was bigger? > + if (IS_ERR(title)) { > + pr_err("failed to strndup .title_uaddr: %d\n", PTR_ERR(title)); > + return -EINVAL; > + } > + > + if (crash_info.msg_uaddr) { > + msg = strndup_user(crash_info.msg_uaddr, PAGE_SIZE); > + if (IS_ERR(msg)) { > + kfree(title); > + pr_err("failed to strndup .msg_uaddr: %d\n", PTR_ERR(msg)); > + return -EINVAL; > + } > + } > + > + ret = do_userpanic(title, msg); > + kfree(msg); > + kfree(title); > + return ret; This can never be hit, right? > + } > + > + return -EINVAL; > +} > + > +static const struct file_operations userpanic_device_fops = { > + .owner = THIS_MODULE, > + .unlocked_ioctl = userpanic_device_ioctl, > + .compat_ioctl = compat_ptr_ioctl, No need for the compat ioctl, do it right the first time. > +}; > + > +static struct miscdevice userpanic_device = { > + .minor = MISC_DYNAMIC_MINOR, > + .name = "userspace_panic", > + .fops = &userpanic_device_fops, > +}; > + > +static int __init userspace_panic_dev_init(void) > +{ > + int ret; > + > + ret = misc_register(&userpanic_device); > + if (ret) > + pr_err("misc_register failed for userspace_panic device\n"); > + > + return ret; > +} Use the correct misc macro here, no need for an init or exit function. Wait, where is your exit function? > +device_initcall(userspace_panic_dev_init); Why this init call level? Why not the normal one? thanks, greg k-h