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SubjectRe: [syzbot] KASAN: slab-out-of-bounds Write in usb_hcd_poll_rh_status (2)
[Trimmed CC: list]

On Thu, Dec 30, 2021 at 04:49:18PM -0800, syzbot wrote:
> Hello,
>
> syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> KASAN: slab-out-of-bounds Write in usb_hcd_poll_rh_status
...
> Tested on:
>
> commit: eec4df26 Merge tag 's390-5.16-6' of git://git.kernel.o..
> git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/

I'm glad to see that the git tree is reported properly, but the commit
label is too short. The reproducer bug report had exactly the opposite
problems! It said:

> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: eec4df26e24e Merge tag 's390-5.16-6' of git://git.kernel.o..
> git tree: upstream

Andrey or Dmitry? Can you guys unify these two outputs to make both
lines correct always?

Moving on... Important lines from the console log:

[ 76.919138][ T4081] usb usb9: usbdev_do_ioctl: BULK
[ 76.924966][ T4081] usb usb9: usbfs: process 4081 (syz-executor189) did not claim interface 0 before use
[ 76.935186][ T4081] usb usb9: ep1 int-in, length 1, timeout 9
[ 76.941355][ T4099] usb usb9: opened by process 4099: syz-executor189
[ 76.942606][ T4087] usb usb9: usbdev_do_ioctl: BULK
[ 76.949968][ C1]
==================================================================
[ 76.950070][ C1] BUG: KASAN: slab-out-of-bounds in usb_hcd_poll_rh_status+0x376/0x780
[ 76.950102][ C1] Write of size 2 at addr ffff8880121ae230 by task syz-executor189/4087

It's hard to tell what's really happening. The suspicious part is the
"length 1" combined with the "Write of size 2" -- but they refer to
different processes!

Maybe this diagnostic patch will help a little.

Alan Stern

#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ eec4df26e24e

Index: usb-devel/drivers/usb/core/devio.c
===================================================================
--- usb-devel.orig/drivers/usb/core/devio.c
+++ usb-devel/drivers/usb/core/devio.c
@@ -109,7 +109,7 @@ struct async {
u8 bulk_status;
};

-static bool usbfs_snoop;
+static bool usbfs_snoop = true;
module_param(usbfs_snoop, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(usbfs_snoop, "true to log all usbfs traffic");

Index: usb-devel/drivers/usb/core/hcd.c
===================================================================
--- usb-devel.orig/drivers/usb/core/hcd.c
+++ usb-devel/drivers/usb/core/hcd.c
@@ -809,8 +809,10 @@ static int rh_queue_status (struct usb_h
unsigned len = 1 + (urb->dev->maxchild / 8);

spin_lock_irqsave (&hcd_root_hub_lock, flags);
+ dev_info(hcd->self.controller, "rh_queue_status: len %d tblen %d\n",
+ len, urb->transfer_buffer_length);
if (hcd->status_urb || urb->transfer_buffer_length < len) {
- dev_dbg (hcd->self.controller, "not queuing rh status urb\n");
+ dev_info(hcd->self.controller, "not queuing rh status urb\n");
retval = -EINVAL;
goto done;
}
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