From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D95E6C433B4 for ; Fri, 9 Apr 2021 09:05:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 954FE61186 for ; Fri, 9 Apr 2021 09:05:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231819AbhDIJFc (ORCPT ); Fri, 9 Apr 2021 05:05:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41708 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230181AbhDIJFc (ORCPT ); Fri, 9 Apr 2021 05:05:32 -0400 Received: from mail-lj1-x229.google.com (mail-lj1-x229.google.com [IPv6:2a00:1450:4864:20::229]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D90BC061761 for ; Fri, 9 Apr 2021 02:05:19 -0700 (PDT) Received: by mail-lj1-x229.google.com with SMTP id p23so1916029ljn.0 for ; Fri, 09 Apr 2021 02:05:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=Diu26lQeyc9P30LZFZqyI13l/S31KxD5z4XWDOuH4g8=; b=qERsISDlAU/QOVO75hzThfBtSMeroZxxnjblbrgURP4R2TDm1x0A7b8Dc27BY0Jtyw UrbSmqFt4gZo47ulHn+1RV7RF7JYmm6OzbUpAIZf3X7SK341PuXhYT3It1fINRnlz6Wi HSpj5ivgzBbRfB9g+uP/d6IbtRfGOMFILLKMyAJ8843uEsVQR8GodsRNZTJ5Mww0aJYw o4+voc/hj6ou6zm8uP+gcCd7hfQ49QBW+Av5UPmc7QpQdoOIG56OZLxnkz34sNKaSy8e dZtN2n47F6NeAY+feM8GVHMmYCwSQiFV60IHITad2s9qs73k3ERomNerayWcRkTzki0v G69w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=Diu26lQeyc9P30LZFZqyI13l/S31KxD5z4XWDOuH4g8=; b=IuH6Dw01Ccq6IMxQLvWihdmSPAT0rcS3d8Uct2CzvGt9enqzBwfRrQXOlPpTKccakJ 3ldCeh+RZQwuZMDjns0zZHx6jrHUWZquWG+CXy3x4z8/S8nVosw/+FqjRAmsDNhX+Ny/ Gitx1bfHf4HgS/XkSAZazSIg4ioIt8oj+PvWMb5FBVIfN7h+9jLeWjmJxkxEUJ4bNA8b qlLKwXBqOTgyCNpUOETkIhdJAz0TMLtdysR+L9tO/k6VFwW/aK7d6f/FOVQj9F8cqcXe 1NWMfdOi1HbFpIuDFbACIoc+eWxKq4CdkB56LCDU6Fb7mSwHoB3l1yUdU3Wz3Gkjad+i kQgw== X-Gm-Message-State: AOAM533NmYc9pEZ+OWJZEiZGI/FDpQhcO3TKGAjiLrEEOogGYIIXmc06 4D1LffRtz6UZTlRj5OEGkDJsUDp+wkHqvPWLnj8VyHjTM8jqfMtl X-Google-Smtp-Source: ABdhPJwaVZc0tYy44wzKUDea7qRugvOw/yWDaetLR7bc9J6yrtNr9rrIY8blj73ciqmYIq9llziS9quXTXF0uV6EiVQ= X-Received: by 2002:a2e:b014:: with SMTP id y20mr8760575ljk.464.1617959117051; Fri, 09 Apr 2021 02:05:17 -0700 (PDT) MIME-Version: 1.0 References: <20210407095527.2771582-1-wak@google.com> In-Reply-To: From: William Kennington Date: Fri, 9 Apr 2021 02:05:05 -0700 Message-ID: Subject: Re: [PATCH] spi: Fix use-after-free with devm_spi_alloc_* To: Andy Shevchenko Cc: "broonie@kernel.org" , "linux-spi@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Joel Stanley Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org For the header file comment? I think it's actually backwards since `devm_allocated =3D true` would indicate the device is managed with devres. Should I send a followup change or v2? On Fri, Apr 9, 2021 at 12:20 AM Andy Shevchenko wrote: > > > > On Wednesday, April 7, 2021, William A. Kennington III w= rote: >> >> We can't rely on the contents of the devres list during >> spi_unregister_controller(), as the list is already torn down at the >> time we perform devres_find() for devm_spi_release_controller. This >> causes devices registered with devm_spi_alloc_{master,slave}() to be >> mistakenly identified as legacy, non-devm managed devices and have their >> reference counters decremented below 0. >> >> ------------[ cut here ]------------ >> WARNING: CPU: 1 PID: 660 at lib/refcount.c:28 refcount_warn_saturate+0x1= 08/0x174 >> [] (refcount_warn_saturate) from [] (kobject_put+0x9= 0/0x98) >> [] (kobject_put) from [] (put_device+0x20/0x24) >> r4:b6700140 >> [] (put_device) from [] (devm_spi_release_controller= +0x3c/0x40) >> [] (devm_spi_release_controller) from [] (release_no= des+0x84/0xc4) >> r5:b6700180 r4:b6700100 >> [] (release_nodes) from [] (devres_release_all+0x5c/= 0x60) >> r8:b1638c54 r7:b117ad94 r6:b1638c10 r5:b117ad94 r4:b163dc10 >> [] (devres_release_all) from [] (__device_release_dr= iver+0x144/0x1ec) >> r5:b117ad94 r4:b163dc10 >> [] (__device_release_driver) from [] (device_driver_= detach+0x84/0xa0) >> r9:00000000 r8:00000000 r7:b117ad94 r6:b163dc54 r5:b1638c10 r4:b163dc10 >> [] (device_driver_detach) from [] (unbind_store+0xe4= /0xf8) >> >> Instead, determine the devm allocation state as a flag on the >> controller which is guaranteed to be stable during cleanup. >> >> Fixes: 5e844cc37a5c ("spi: Introduce device-managed SPI controller alloc= ation") >> Signed-off-by: William A. Kennington III >> --- >> drivers/spi/spi.c | 9 ++------- >> include/linux/spi/spi.h | 3 +++ >> 2 files changed, 5 insertions(+), 7 deletions(-) >> >> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c >> index b08efe88ccd6..904a353798b6 100644 >> --- a/drivers/spi/spi.c >> +++ b/drivers/spi/spi.c >> @@ -2496,6 +2496,7 @@ struct spi_controller *__devm_spi_alloc_controller= (struct device *dev, >> >> ctlr =3D __spi_alloc_controller(dev, size, slave); >> if (ctlr) { >> + ctlr->devm_allocated =3D true; >> *ptr =3D ctlr; >> devres_add(dev, ptr); >> } else { >> @@ -2842,11 +2843,6 @@ int devm_spi_register_controller(struct device *d= ev, >> } >> EXPORT_SYMBOL_GPL(devm_spi_register_controller); >> >> -static int devm_spi_match_controller(struct device *dev, void *res, voi= d *ctlr) >> -{ >> - return *(struct spi_controller **)res =3D=3D ctlr; >> -} >> - >> static int __unregister(struct device *dev, void *null) >> { >> spi_unregister_device(to_spi_device(dev)); >> @@ -2893,8 +2889,7 @@ void spi_unregister_controller(struct spi_controll= er *ctlr) >> /* Release the last reference on the controller if its driver >> * has not yet been converted to devm_spi_alloc_master/slave(). >> */ >> - if (!devres_find(ctlr->dev.parent, devm_spi_release_controller, >> - devm_spi_match_controller, ctlr)) >> + if (!ctlr->devm_allocated) >> put_device(&ctlr->dev); >> >> /* free bus id */ >> diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h >> index 592897fa4f03..643139b1eafe 100644 >> --- a/include/linux/spi/spi.h >> +++ b/include/linux/spi/spi.h >> @@ -510,6 +510,9 @@ struct spi_controller { >> >> #define SPI_MASTER_GPIO_SS BIT(5) /* GPIO CS must select s= lave */ >> >> + /* flag indicating this is a non-devres managed controller */ > > > > Isn=E2=80=99t =E2=80=9Cnon-=E2=80=9C part confusing a lot? > >> >> + bool devm_allocated; >> + >> /* flag indicating this is an SPI slave controller */ >> bool slave; >> >> -- >> 2.31.0.208.g409f899ff0-goog >> > > > -- > With Best Regards, > Andy Shevchenko > >