linux-fbdev.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Hyunwoo Kim <imv4bel@gmail.com>
To: steve.glendinning@shawell.net, deller@gmx.de
Cc: linux-fbdev@vger.kernel.org, dri-devel@lists.freedesktop.org,
	imv4bel@gmail.com
Subject: [PATCH v3] video: fbdev: smscufx: Fix use-after-free in ufx_ops_open()
Date: Sun, 25 Sep 2022 06:32:43 -0700	[thread overview]
Message-ID: <20220925133243.GA383897@ubuntu> (raw)

A race condition may occur if the user physically removes the
USB device while calling open() for this device node.

This is a race condition between the ufx_ops_open() function and
the ufx_usb_disconnect() function, which may eventually result in UAF.

So, add a mutex to the ufx_ops_open() and ufx_usb_disconnect() functions
to avoid race contidion of krefs.

Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
---
 drivers/video/fbdev/smscufx.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/smscufx.c b/drivers/video/fbdev/smscufx.c
index d7aa5511c361..e65bdc499c23 100644
--- a/drivers/video/fbdev/smscufx.c
+++ b/drivers/video/fbdev/smscufx.c
@@ -137,6 +137,8 @@ static int ufx_submit_urb(struct ufx_data *dev, struct urb * urb, size_t len);
 static int ufx_alloc_urb_list(struct ufx_data *dev, int count, size_t size);
 static void ufx_free_urb_list(struct ufx_data *dev);
 
+static DEFINE_MUTEX(disconnect_mutex);
+
 /* reads a control register */
 static int ufx_reg_read(struct ufx_data *dev, u32 index, u32 *data)
 {
@@ -1071,9 +1073,13 @@ static int ufx_ops_open(struct fb_info *info, int user)
 	if (user == 0 && !console)
 		return -EBUSY;
 
+	mutex_lock(&disconnect_mutex);
+
 	/* If the USB device is gone, we don't accept new opens */
-	if (dev->virtualized)
+	if (dev->virtualized) {
+		mutex_unlock(&disconnect_mutex);
 		return -ENODEV;
+	}
 
 	dev->fb_count++;
 
@@ -1097,6 +1103,8 @@ static int ufx_ops_open(struct fb_info *info, int user)
 	pr_debug("open /dev/fb%d user=%d fb_info=%p count=%d",
 		info->node, user, info, dev->fb_count);
 
+	mutex_unlock(&disconnect_mutex);
+
 	return 0;
 }
 
@@ -1741,6 +1749,8 @@ static void ufx_usb_disconnect(struct usb_interface *interface)
 {
 	struct ufx_data *dev;
 
+	mutex_lock(&disconnect_mutex);
+
 	dev = usb_get_intfdata(interface);
 
 	pr_debug("USB disconnect starting\n");
@@ -1761,6 +1771,8 @@ static void ufx_usb_disconnect(struct usb_interface *interface)
 	kref_put(&dev->kref, ufx_free);
 
 	/* consider ufx_data freed */
+
+	mutex_unlock(&disconnect_mutex);
 }
 
 static struct usb_driver ufx_driver = {
-- 
2.25.1


             reply	other threads:[~2022-09-25 13:32 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-25 13:32 Hyunwoo Kim [this message]
2022-09-25 15:47 ` [PATCH v3] video: fbdev: smscufx: Fix use-after-free in ufx_ops_open() Helge Deller
2022-09-26  4:50   ` Hyunwoo Kim

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=20220925133243.GA383897@ubuntu \
    --to=imv4bel@gmail.com \
    --cc=deller@gmx.de \
    --cc=dri-devel@lists.freedesktop.org \
    --cc=linux-fbdev@vger.kernel.org \
    --cc=steve.glendinning@shawell.net \
    /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).