From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 8 Nov 2021 15:35:50 +0100 From: Borislav Petkov Subject: Re: [PATCH v0 00/42] notifiers: Return an error when callback is already registered Message-ID: References: <20211108101157.15189-1-bp@alien8.de> <20211108101924.15759-1-bp@alien8.de> <20211108141703.GB1666297@rowland.harvard.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: To: Alan Stern , Geert Uytterhoeven Cc: LKML , Arnd Bergmann , Ayush Sawal , Greg Kroah-Hartman , Rohit Maheshwari , Steven Rostedt , Vinay Kumar Yadav , alsa-devel@alsa-project.org, bcm-kernel-feedback-list@broadcom.com, intel-gfx@lists.freedesktop.org, intel-gvt-dev@lists.freedesktop.org, linux-alpha@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org, linux-crypto@vger.kernel.org, linux-edac@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-iio@vger.kernel.org, linux-leds@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-pm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-remoteproc@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-s390@vger.kernel.org, linux-scsi@vger.kernel.org, linux-sh@vger.kernel.org, linux-staging@lists.linux.dev, linux-tegra@vger.kernel.org, linux-um@lists.infradead.org, linux-usb@vger.kernel.org, linux-xtensa@linux-xtensa.org, netdev@vger.kernel.org, openipmi-developer@lists.sourceforge.net, rcu@vger.kernel.org, sparclinux@vger.kernel.org, x86@kernel.org, xen-devel@lists.xenproject.org List-ID: On Mon, Nov 08, 2021 at 03:24:39PM +0100, Borislav Petkov wrote: > I guess I can add another indirection to notifier_chain_register() and > avoid touching all the call sites. IOW, something like this below. This way I won't have to touch all the callsites and the registration routines would still return a proper value instead of returning 0 unconditionally. --- diff --git a/kernel/notifier.c b/kernel/notifier.c index b8251dc0bc0f..04f08b2ef17f 100644 --- a/kernel/notifier.c +++ b/kernel/notifier.c @@ -19,14 +19,12 @@ BLOCKING_NOTIFIER_HEAD(reboot_notifier_list); * are layered on top of these, with appropriate locking added. */ -static int notifier_chain_register(struct notifier_block **nl, - struct notifier_block *n) +static int __notifier_chain_register(struct notifier_block **nl, + struct notifier_block *n) { while ((*nl) != NULL) { - if (unlikely((*nl) == n)) { - WARN(1, "double register detected"); - return 0; - } + if (unlikely((*nl) == n)) + return -EEXIST; if (n->priority > (*nl)->priority) break; nl = &((*nl)->next); @@ -36,6 +34,18 @@ static int notifier_chain_register(struct notifier_block **nl, return 0; } +static int notifier_chain_register(struct notifier_block **nl, + struct notifier_block *n) +{ + int ret = __notifier_chain_register(nl, n); + + if (ret == -EEXIST) + WARN(1, "double register of notifier callback %ps detected", + n->notifier_call); + + return ret; +} + static int notifier_chain_unregister(struct notifier_block **nl, struct notifier_block *n) { -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette