linux-kernel - Re: KASAN: use-after-free Read in si470x_int_in

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Message-ID: <1574939450.21204.7.camel@suse.com>
Date:   Thu, 28 Nov 2019 12:10:50 +0100
From:   Oliver Neukum <oneukum@...e.com>
To:     syzbot <syzbot+9ca7a12fd736d93e0232@...kaller.appspotmail.com>,
        andreyknvl@...gle.com, hverkuil@...all.nl,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-usb@...r.kernel.org, mchehab@...nel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: KASAN: use-after-free Read in si470x_int_in_callback (2)

Am Freitag, den 18.10.2019, 07:53 -0700 schrieb syzbot:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    22be26f7 usb-fuzzer: main usb gadget fuzzer driver
> git tree:       https://github.com/google/kasan.git usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=102b65cf600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=387eccb7ac68ec5
> dashboard link: https://syzkaller.appspot.com/bug?extid=9ca7a12fd736d93e0232
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=143b9060e00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15d3b94b600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+9ca7a12fd736d93e0232@...kaller.appspotmail.com

JUST FOR DEBUGGING

#syz test: https://github.com/google/kasan.git 22be26f7

>From 6e4c324c34b2fead2bdd1bc1274bd2e978df2be5 Mon Sep 17 00:00:00 2001
From: Oliver Neukum <oneukum@...e.com>
Date: Mon, 18 Nov 2019 14:41:51 +0100
Subject: [PATCH] si470x: prevent resubmission

Starting IO to a device is not necessarily a NOP in every error
case. So we need to terminate all IO in every case of probe
failure and disconnect with absolute certainty.

Signed-off-by: Oliver Neukum <oneukum@...e.com>
---
 drivers/media/radio/si470x/radio-si470x-usb.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/media/radio/si470x/radio-si470x-usb.c b/drivers/media/radio/si470x/radio-si470x-usb.c
index fedff68d8c49..3a3c539ee39a 100644
--- a/drivers/media/radio/si470x/radio-si470x-usb.c
+++ b/drivers/media/radio/si470x/radio-si470x-usb.c
@@ -373,6 +373,7 @@ static void si470x_int_in_callback(struct urb *urb)
 		if (urb->status == -ENOENT ||
 				urb->status == -ECONNRESET ||
 				urb->status == -ESHUTDOWN) {
+			printk(KERN_ERR"Int URB killed\n");
 			return;
 		} else {
 			dev_warn(&radio->intf->dev,
@@ -463,6 +464,7 @@ static void si470x_int_in_callback(struct urb *urb)
 	/* Resubmit if we're still running. */
 	if (radio->int_in_running && radio->usbdev) {
 		retval = usb_submit_urb(radio->int_in_urb, GFP_ATOMIC);
+		printk(KERN_ERR"In resubmit code path with result %d\n", retval);
 		if (retval) {
 			dev_warn(&radio->intf->dev,
 			       "resubmitting urb failed (%d)", retval);
@@ -542,6 +544,8 @@ static int si470x_start_usb(struct si470x_device *radio)
 		radio->int_in_running = 0;
 	}
 	radio->status_rssi_auto_update = radio->int_in_running;
+	if (retval < 0)
+		return retval;
 
 	/* start radio */
 	retval = si470x_start(radio);
@@ -734,7 +738,8 @@ static int si470x_usb_driver_probe(struct usb_interface *intf,
 	/* start radio */
 	retval = si470x_start_usb(radio);
 	if (retval < 0)
-		goto err_buf;
+		/* the urb may be running even after an error */
+		goto err_all;
 
 	/* set initial frequency */
 	si470x_set_freq(radio, 87.5 * FREQ_MUL); /* available in all regions */
@@ -749,7 +754,7 @@ static int si470x_usb_driver_probe(struct usb_interface *intf,
 
 	return 0;
 err_all:
-	usb_kill_urb(radio->int_in_urb);
+	usb_poison_urb(radio->int_in_urb);
 err_buf:
 	kfree(radio->buffer);
 err_ctrl:
@@ -824,7 +829,7 @@ static void si470x_usb_driver_disconnect(struct usb_interface *intf)
 	mutex_lock(&radio->lock);
 	v4l2_device_disconnect(&radio->v4l2_dev);
 	video_unregister_device(&radio->videodev);
-	usb_kill_urb(radio->int_in_urb);
+	usb_poison_urb(radio->int_in_urb);
 	usb_set_intfdata(intf, NULL);
 	mutex_unlock(&radio->lock);
 	v4l2_device_put(&radio->v4l2_dev);
-- 
2.16.4