From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from frasgout11.his.huawei.com (frasgout11.his.huawei.com [14.137.139.23]) (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 40EEF12AADB for ; Thu, 7 Mar 2024 12:43:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=14.137.139.23 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709815439; cv=none; b=RGvLT9sqhl50buF/yqtZI/qsDDYxfL1WzjpoVGuVZYb/Up2O/tyv5FY7rw4aAKDbX8vrpZZ4NJtAIkMtpG8Geszf+aBcoFRGvkMJrBh/8QHahI3Du8jWXP/PkTQ8SY5bdX9nD8WUjWYRRxMh+MqArL0XCML+S/ZMDEzHQWLOhm0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709815439; c=relaxed/simple; bh=+5k+8rEgISBNGB59KLCG2aMKGbsCMx3Ul6Z2Iblf7J0=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=J63WIoCJL9WrnP9yweda2qRA5R6Rk1VUgPZpzZgOdod4A8sDqG80PALVO/Lir7oczGwB7c4L5p7Mj8qnlSTGY/aYJBMwNFjj0RwND/2bVgo6j1wWLCRpmlHXgn0doYLW2OWJf0/KzE5BC/nni91dr2yMQhH9dPr5pssI/iejdKE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=14.137.139.23 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.18.186.29]) by frasgout11.his.huawei.com (SkyGuard) with ESMTP id 4Tr7qs4Kmxz9xHw5 for ; Thu, 7 Mar 2024 20:28:09 +0800 (CST) Received: from mail02.huawei.com (unknown [7.182.16.47]) by mail.maildlp.com (Postfix) with ESMTP id 24626140154 for ; Thu, 7 Mar 2024 20:43:52 +0800 (CST) Received: from [127.0.0.1] (unknown [10.204.63.22]) by APP1 (Coremail) with SMTP id LxC2BwBXTBWAtullIlHjAw--.4316S2; Thu, 07 Mar 2024 13:43:51 +0100 (CET) Message-ID: <2d70513e9f84e650ef1ede5a8ae5960a9de782bc.camel@huaweicloud.com> Subject: Re: [PATCH] um: Add winch to winch_handlers before registering winch IRQ From: Roberto Sassu To: richard@nod.at, anton.ivanov@cambridgegreys.com, johannes@sipsolutions.net Cc: linux-kernel@vger.kernel.org, linux-um@lists.infradead.org, Roberto Sassu Date: Thu, 07 Mar 2024 13:43:40 +0100 In-Reply-To: <20240307104926.3531358-1-roberto.sassu@huaweicloud.com> References: <20240307104926.3531358-1-roberto.sassu@huaweicloud.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.44.4-0ubuntu2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-CM-TRANSID:LxC2BwBXTBWAtullIlHjAw--.4316S2 X-Coremail-Antispam: 1UD129KBjvJXoW7tF45Jr4fCF4UAFWDZFW3Awb_yoW8uFW5pF WagFnavrWSqa10ganrJa1qyFWxAws7Gr1Uur1kK345ZryUXr9aqF1rGa42qF1DAry7Jr93 Xr4F9a9xuayDAwUanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUgCb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4 vEj48ve4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_Jr0_JF4l84ACjcxK6xIIjxv20xvEc7Cj xVAFwI0_Jr0_Gr1l84ACjcxK6I8E87Iv67AKxVW8JVWxJwA2z4x0Y4vEx4A2jsIEc7CjxV AFwI0_Gr1j6F4UJwAS0I0E0xvYzxvE52x082IY62kv0487Mc02F40EFcxC0VAKzVAqx4xG 6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAFwI0_Jr0_Gr1lOx8S6xCaFV Cjc4AY6r1j6r4UM4x0Y48IcVAKI48JMxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY 6r1j6r4UMI8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17 CEb7AF67AKxVWUAVWUtwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF 0xvE2Ix0cI8IcVCY1x0267AKxVWUJVW8JwCI42IY6xAIw20EY4v20xvaj40_Wr1j6rW3Jr 1lIxAIcVC2z280aVAFwI0_Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsG vfC2KfnxnUUI43ZEXa7IU1zuWJUUUUU== X-CM-SenderInfo: purev21wro2thvvxqx5xdzvxpfor3voofrz/1tbiAQAPBF1jj5sXFwABsh On Thu, 2024-03-07 at 11:49 +0100, Roberto Sassu wrote: > From: Roberto Sassu >=20 > Registering a winch IRQ is racy, an interrupt may occur before the winch = is > added to the winch_handlers list. >=20 > If that happens, register_winch_irq() adds to that list a winch that is > scheduled to be (or has already been) freed, causing a panic later in > winch_cleanup(). >=20 > Avoid the race by adding the winch to the winch_handlers list before > registering the IRQ, and rolling back if um_request_irq() fails. >=20 > Signed-off-by: Roberto Sassu Fixes: 42a359e31a0e ("uml: SIGIO support cleanup") I see that before that commit there was the same ordering (list_add() before um_request_irq()). Failure from um_request_irq() should not result in executing winch_interrupt() which could call list_del() itself. Then, it should be fine to delete the winch in the error path. Roberto > --- > arch/um/drivers/line.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) >=20 > diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c > index ffc5cb92fa36..d82bc3fdb86e 100644 > --- a/arch/um/drivers/line.c > +++ b/arch/um/drivers/line.c > @@ -676,24 +676,26 @@ void register_winch_irq(int fd, int tty_fd, int pid= , struct tty_port *port, > goto cleanup; > } > =20 > - *winch =3D ((struct winch) { .list =3D LIST_HEAD_INIT(winch->list), > - .fd =3D fd, > + *winch =3D ((struct winch) { .fd =3D fd, > .tty_fd =3D tty_fd, > .pid =3D pid, > .port =3D port, > .stack =3D stack }); > =20 > + spin_lock(&winch_handler_lock); > + list_add(&winch->list, &winch_handlers); > + spin_unlock(&winch_handler_lock); > + > if (um_request_irq(WINCH_IRQ, fd, IRQ_READ, winch_interrupt, > IRQF_SHARED, "winch", winch) < 0) { > printk(KERN_ERR "register_winch_irq - failed to register " > "IRQ\n"); > + spin_lock(&winch_handler_lock); > + list_del(&winch->list); > + spin_unlock(&winch_handler_lock); > goto out_free; > } > =20 > - spin_lock(&winch_handler_lock); > - list_add(&winch->list, &winch_handlers); > - spin_unlock(&winch_handler_lock); > - > return; > =20 > out_free: