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SubjectRe: KASAN: use-after-free Read in dvb_usb_device_exit
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On Fr, 2019-04-12 at 04:46 -0700, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 9a33b369 usb-fuzzer: main usb gadget fuzzer driver
> git tree: https://github.com/google/kasan/tree/usb-fuzzer
> console output: https://syzkaller.appspot.com/x/log.txt?x=1643974b200000
> kernel config: https://syzkaller.appspot.com/x/.config?x=23e37f59d94ddd15
> dashboard link: https://syzkaller.appspot.com/bug?extid=26ec41e9f788b3eba396
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12f5efa7200000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1395a0f3200000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+26ec41e9f788b3eba396@syzkaller.appspotmail.com
>
> dvb-usb: schedule remote query interval to 150 msecs.
> dw2102: su3000_power_ctrl: 0, initialized 1
> dvb-usb: TeVii S421 PCI successfully initialized and connected.
> usb 1-1: USB disconnect, device number 2

Hi,

proposed fix. If nobody objects, I will submit it.

Regards
Oliver

From d6097d205ac61745334b79639d3b8b910ae66c71 Mon Sep 17 00:00:00 2001
From: Oliver Neukum <oneukum@suse.com>
Date: Mon, 15 Apr 2019 13:06:01 +0200
Subject: [PATCH] dvb: usb: fix use after free in dvb_usb_device_exit

dvb_usb_device_exit() frees and uses teh device name in that order
Fix by storing the name in a buffer before freeing it

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Reported-by: syzbot+26ec41e9f788b3eba396@syzkaller.appspotmail.com
---
drivers/media/usb/dvb-usb/dvb-usb-init.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/dvb-usb/dvb-usb-init.c b/drivers/media/usb/dvb-usb/dvb-usb-init.c
index 99951e02a880..2e1670cc3903 100644
--- a/drivers/media/usb/dvb-usb/dvb-usb-init.c
+++ b/drivers/media/usb/dvb-usb/dvb-usb-init.c
@@ -288,13 +288,18 @@ void dvb_usb_device_exit(struct usb_interface *intf)
{
struct dvb_usb_device *d = usb_get_intfdata(intf);
const char *name = "generic DVB-USB module";
+ char identifier[40];

usb_set_intfdata(intf, NULL);
if (d != NULL && d->desc != NULL) {
name = d->desc->name;
+ memcpy(identifier, name, 39);
+ identifier[39] = NULL;
dvb_usb_exit(d);
+ } else {
+ memcpy(identifier, name, 39);
}
- info("%s successfully deinitialized and disconnected.", name);
+ info("%s successfully deinitialized and disconnected.", identifier);

}
EXPORT_SYMBOL(dvb_usb_device_exit);
--
2.16.4
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