Re: KASAN: use-after-free Read in usbhid_power

[Oliver Neukum <oneukum@suse.com>]

Am Dienstag, den 23.07.2019, 05:48 -0700 schrieb syzbot:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    6a3599ce 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=11b13e78600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=700ca426ab83faae
> dashboard link: https://syzkaller.appspot.com/bug?extid=ef5de9c4f99c4edb4e49
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15482210600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1139b07c600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+ef5de9c4f99c4edb4e49@syzkaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: use-after-free in usbhid_power+0xca/0xe0  
> /drivers/hid/usbhid/hid-core.c:1234
> Read of size 8 at addr ffff8881ce8a4008 by task syz-executor373/1763

#syz test: https://github.com/google/kasan.git usb-fuzzer-usb-testing-2019.07.11

From a3455c4527bdfe86536856ea96288b7dcc36590b Mon Sep 17 00:00:00 2001
From: Oliver Neukum <oneukum@suse.com>
Date: Wed, 24 Jul 2019 22:49:57 +0200
Subject: [PATCH] usbhid: test for disconnected state in raw opening

If the device has been disconnected, we should not proceed to use
runtime PM on it.

Reported-by: syzbot+ef5de9c4f99c4edb4e49@syzkaller.appspotmail.com
Signed-off-by: Oliver Neukum <oneukum@suse.de>
---
 drivers/hid/usbhid/hid-core.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
index c7bc9db5b192..98b996ecf4d3 100644
--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c
@@ -1229,6 +1229,17 @@ static int usbhid_power(struct hid_device *hid, int lvl)
 	struct usbhid_device *usbhid = hid->driver_data;
 	int r = 0;
 
+	spin_lock_irq(&usbhid->lock);
+	if (test_bit(HID_DISCONNECTED, &usbhid->iofl)) {
+		r = -ENODEV;
+		spin_unlock_irq(&usbhid->lock);
+		goto bail_out;
+	} else {
+		/* protect against disconnect */
+		usb_get_dev(interface_to_usbdev(usbhid->intf));
+		spin_unlock_irq(&usbhid->lock);
+	}
+
 	switch (lvl) {
 	case PM_HINT_FULLON:
 		r = usb_autopm_get_interface(usbhid->intf);
@@ -1238,7 +1249,9 @@ static int usbhid_power(struct hid_device *hid, int lvl)
 		usb_autopm_put_interface(usbhid->intf);
 		break;
 	}
+	usb_put_dev(interface_to_usbdev(usbhid->intf));
 
+bail_out:
 	return r;
 }