From: Greg KH <gregkh@linuxfoundation.org>
To: Adrian Salido <salidoa@google.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] driver core: platform: fix race condition with driver_override
Date: Wed, 26 Apr 2017 13:57:59 +0200 [thread overview]
Message-ID: <20170426115759.GB8813@kroah.com> (raw)
In-Reply-To: <20170425235526.GA165155@google.com>
On Tue, Apr 25, 2017 at 04:55:26PM -0700, Adrian Salido wrote:
> The driver_override implementation is susceptible to race condition when
> different threads are reading vs storing a different driver override.
> Add locking to avoid race condition.
>
> Fixes: 3d713e0e382e ("driver core: platform: add device binding path 'driver_override'")
> Cc: stable@vger.kernel.org
> Signed-off-by: Adrian Salido <salidoa@google.com>
> ---
> drivers/base/platform.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index c2456839214a..493e03fa0e07 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -866,7 +866,7 @@ static ssize_t driver_override_store(struct device *dev,
> const char *buf, size_t count)
> {
> struct platform_device *pdev = to_platform_device(dev);
> - char *driver_override, *old = pdev->driver_override, *cp;
> + char *driver_override, *old, *cp;
>
> if (count > PATH_MAX)
> return -EINVAL;
> @@ -879,12 +879,15 @@ static ssize_t driver_override_store(struct device *dev,
> if (cp)
> *cp = '\0';
>
> + device_lock(dev);
> + old = pdev->driver_override;
> if (strlen(driver_override)) {
> pdev->driver_override = driver_override;
> } else {
> kfree(driver_override);
> pdev->driver_override = NULL;
> }
> + device_unlock(dev);
>
> kfree(old);
Shouldn't you move the lock until after the kfree()? Or am I missing
what the lock is trying to protect here?
>
> @@ -895,8 +898,12 @@ static ssize_t driver_override_show(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> struct platform_device *pdev = to_platform_device(dev);
> + ssize_t len;
>
> - return sprintf(buf, "%s\n", pdev->driver_override);
> + device_lock(dev);
> + len = sprintf(buf, "%s\n", pdev->driver_override);
> + device_unlock(dev);
> + return len;
Why does the show function need to be changed at all? How can anything
"race" here?
thanks,
greg k-h
next prev parent reply other threads:[~2017-04-26 11:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-25 23:55 [PATCH] driver core: platform: fix race condition with driver_override Adrian Salido
2017-04-26 11:57 ` Greg KH [this message]
2017-04-26 14:51 ` Adrian Salido
2017-04-26 15:48 ` Greg KH
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170426115759.GB8813@kroah.com \
--to=gregkh@linuxfoundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=salidoa@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).