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Message-ID: <Pine.LNX.4.44L0.1909191639240.6904-100000@iolanthe.rowland.org>
Date: Thu, 19 Sep 2019 16:43:08 -0400 (EDT)
From: Alan Stern <stern@...land.harvard.edu>
To: syzbot <syzbot+745b0dff8028f9488eba@...kaller.appspotmail.com>
cc: andreyknvl@...gle.com, <gregkh@...uxfoundation.org>,
<linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>,
<miquel@...uba.ar>, <rio500-users@...ts.sourceforge.net>,
<syzkaller-bugs@...glegroups.com>
Subject: Re: KASAN: invalid-free in disconnect_rio (2)
On Thu, 19 Sep 2019, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: e0bd8d79 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=17d6f31d600000
> kernel config: https://syzkaller.appspot.com/x/.config?x=8847e5384a16f66a
> dashboard link: https://syzkaller.appspot.com/bug?extid=745b0dff8028f9488eba
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1009f769600000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15b1d4b1600000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+745b0dff8028f9488eba@...kaller.appspotmail.com
>
> usb 5-1: New USB device found, idVendor=0841, idProduct=0001,
> bcdDevice=c5.d0
> usb 5-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
> usb 5-1: config 0 descriptor??
> rio500 5-1:0.133: Second USB Rio at address 2 refused
> rio500: probe of 5-1:0.133 failed with error -16
> usb 3-1: USB disconnect, device number 2
> ==================================================================
> BUG: KASAN: double-free or invalid-free in disconnect_rio+0x12b/0x1b0
> drivers/usb/misc/rio500.c:525
All right, that was a pretty dumb mistake on my part. Checking for
whether a device has already been registered needs to be part of the
critical section.
Alan Stern
#syz test: https://github.com/google/kasan.git e0bd8d79
drivers/usb/misc/rio500.c | 34 ++++++++++++++++++----------------
1 file changed, 18 insertions(+), 16 deletions(-)
Index: usb-devel/drivers/usb/misc/rio500.c
===================================================================
--- usb-devel.orig/drivers/usb/misc/rio500.c
+++ usb-devel/drivers/usb/misc/rio500.c
@@ -454,36 +454,35 @@ static int probe_rio(struct usb_interfac
{
struct usb_device *dev = interface_to_usbdev(intf);
struct rio_usb_data *rio = &rio_instance;
- int retval = -ENOMEM;
- char *ibuf, *obuf;
+ int retval;
+ mutex_lock(&rio500_mutex);
if (rio->present) {
dev_info(&intf->dev, "Second USB Rio at address %d refused\n", dev->devnum);
- return -EBUSY;
+ retval = -EBUSY;
+ goto err_present;
}
dev_info(&intf->dev, "USB Rio found at address %d\n", dev->devnum);
+ rio->present = 1;
- obuf = kmalloc(OBUF_SIZE, GFP_KERNEL);
- if (!obuf) {
+ retval = -ENOMEM;
+ rio->obuf = kmalloc(OBUF_SIZE, GFP_KERNEL);
+ if (!rio->obuf) {
dev_err(&dev->dev,
"probe_rio: Not enough memory for the output buffer\n");
goto err_obuf;
}
- dev_dbg(&intf->dev, "obuf address: %p\n", obuf);
+ dev_dbg(&intf->dev, "obuf address: %p\n", rio->obuf);
- ibuf = kmalloc(IBUF_SIZE, GFP_KERNEL);
- if (!ibuf) {
+ rio->ibuf = kmalloc(IBUF_SIZE, GFP_KERNEL);
+ if (!rio->ibuf) {
dev_err(&dev->dev,
"probe_rio: Not enough memory for the input buffer\n");
goto err_ibuf;
}
- dev_dbg(&intf->dev, "ibuf address: %p\n", ibuf);
+ dev_dbg(&intf->dev, "ibuf address: %p\n", rio->ibuf);
- mutex_lock(&rio500_mutex);
rio->rio_dev = dev;
- rio->ibuf = ibuf;
- rio->obuf = obuf;
- rio->present = 1;
mutex_unlock(&rio500_mutex);
retval = usb_register_dev(intf, &usb_rio_class);
@@ -498,11 +497,14 @@ static int probe_rio(struct usb_interfac
err_register:
mutex_lock(&rio500_mutex);
- rio->present = 0;
- mutex_unlock(&rio500_mutex);
+ rio->rio_dev = NULL;
+ kfree(rio->ibuf);
err_ibuf:
- kfree(obuf);
+ kfree(rio->obuf);
err_obuf:
+ rio->present = 0;
+ err_present:
+ mutex_unlock(&rio500_mutex);
return retval;
}
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