From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1524671770; cv=none; d=google.com; s=arc-20160816; b=mPJJr3bQxqbzVbLiW5bZwKEl1SX8pxbOec7ipLrDww1YmkZZrKmbndR8v6X+jaYv5v FTY5CsBo4yp4NJMmJCPLA4ugAp8vmhPf1/L5z52li2HZGvvIF/yX+T+tVScwLnV3rO7Y ZcE3wSUyPJOas9lc6+p/hSmvJoSvY8igufxrIJ/y97cigourEDo2S3l6laML4XrvFhLl umWB/TDJQn57os6J2rSiwZtyZM9Dh7CABDm6HzBZWbYufpfrE5KHWlBGEY3GwXixFluY VHOW6ZPv6AZhGuIrDfdOZ4VyxqMSa563PUW1ZS13vb63FetuM3Hkne3x8flYez5SL14g WqhQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=cc:to:subject:message-id:date:from:references:in-reply-to :mime-version:dkim-signature:arc-authentication-results; bh=3+FdJP1qLXrXsMILF6YY4ciuj+34BbYQhRH801gUGwA=; b=ymYgmWrNJSfcNaw4yiU36W49M8QgE1fsXUE0HANoCnUfSSrQwGhxk5Fl8N43KTvkPP dVcBcTm0oRIwPTZbaD1mo3aXqZdeUfOUXR2v4ZehfkPfvoDk28Fx4w2U/LobmXfoepHT G/1mZBaNlvyNBVA7CJubfVZX1z6o8HsUgwS46pGanEiPMK/ot2LmcpXcZ4XkIls5aiUL GIr5LCv22eQR9O0vfDYMd07jo2l0jLTun0aTZhuio8E00cS5qQpo8luzB0oiZW0P2FYn fegwd/mUZ7w1AuKOnXoGximAqe32sAPYqmfQb47+rLo89x+H+djHkVDE7RvSZkjnmyie TD9Q== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@android.com header.s=20161025 header.b=rydZ5Woj; spf=pass (google.com: domain of tkjos@android.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=tkjos@android.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=android.com Authentication-Results: mx.google.com; dkim=pass header.i=@android.com header.s=20161025 header.b=rydZ5Woj; spf=pass (google.com: domain of tkjos@android.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=tkjos@android.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=android.com X-Google-Smtp-Source: AIpwx49LUxh/h/IHzfpyD2tPXHT8CRTNhbPPFxu0bnb2wieTbTXyguMg328UwK9QtEIONIgmZuY5AtqRBcR7nfXFpQA= MIME-Version: 1.0 In-Reply-To: <1523366506-19832-3-git-send-email-geert+renesas@glider.be> References: <1523366506-19832-1-git-send-email-geert+renesas@glider.be> <1523366506-19832-3-git-send-email-geert+renesas@glider.be> From: Todd Kjos Date: Wed, 25 Apr 2018 08:56:09 -0700 Message-ID: Subject: Re: [PATCH v2 2/4] ARM: amba: Fix race condition with driver_override To: Geert Uytterhoeven Cc: Greg Kroah-Hartman , Russell King , Adrian Salido , Nicolai Stange , Sasha Levin , LKML Content-Type: text/plain; charset="UTF-8" X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1597365566189003865?= X-GMAIL-MSGID: =?utf-8?q?1598734226056005068?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Reviewed-by: Todd Kjos On Tue, Apr 10, 2018 at 6:21 AM, Geert Uytterhoeven wrote: > The driver_override implementation is susceptible to a race condition > when different threads are reading vs storing a different driver > override. Add locking to avoid this race condition. > > Cfr. commits 6265539776a0810b ("driver core: platform: fix race > condition with driver_override") and 9561475db680f714 ("PCI: Fix race > condition with driver_override"). > > Fixes: 3cf385713460eb2b ("ARM: 8256/1: driver coamba: add device binding path 'driver_override'") > Signed-off-by: Geert Uytterhoeven > --- > drivers/amba/bus.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c > index 6ffd778352e6d953..36c5653ced5742b7 100644 > --- a/drivers/amba/bus.c > +++ b/drivers/amba/bus.c > @@ -69,8 +69,12 @@ static ssize_t driver_override_show(struct device *_dev, > struct device_attribute *attr, char *buf) > { > struct amba_device *dev = to_amba_device(_dev); > + ssize_t len; > > - return sprintf(buf, "%s\n", dev->driver_override); > + device_lock(_dev); > + len = sprintf(buf, "%s\n", dev->driver_override); > + device_unlock(_dev); > + return len; > } > > static ssize_t driver_override_store(struct device *_dev, > @@ -78,7 +82,7 @@ static ssize_t driver_override_store(struct device *_dev, > const char *buf, size_t count) > { > struct amba_device *dev = to_amba_device(_dev); > - char *driver_override, *old = dev->driver_override, *cp; > + char *driver_override, *old, *cp; > > if (count > PATH_MAX) > return -EINVAL; > @@ -91,12 +95,15 @@ static ssize_t driver_override_store(struct device *_dev, > if (cp) > *cp = '\0'; > > + device_lock(_dev); > + old = dev->driver_override; > if (strlen(driver_override)) { > dev->driver_override = driver_override; > } else { > kfree(driver_override); > dev->driver_override = NULL; > } > + device_unlock(_dev); > > kfree(old); > > -- > 2.7.4 >