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SubjectRe: KASAN: slab-out-of-bounds Read in usb_reset_and_verify_device
On Tue, 3 Sep 2019, syzbot wrote:

> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: eea39f24 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=174761b6600000
> kernel config: https://syzkaller.appspot.com/x/.config?x=d0c62209eedfd54e
> dashboard link: https://syzkaller.appspot.com/bug?extid=35f4d916c623118d576e
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1706275a600000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+35f4d916c623118d576e@syzkaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in memcmp+0xa6/0xb0 lib/string.c:904
> Read of size 1 at addr ffff8881d175bed6 by task kworker/0:3/2746
>
> CPU: 0 PID: 2746 Comm: kworker/0:3 Not tainted 5.3.0-rc5+ #28
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Workqueue: usb_hub_wq hub_event
> Call Trace:
> __dump_stack lib/dump_stack.c:77 [inline]
> dump_stack+0xca/0x13e lib/dump_stack.c:113
> print_address_description+0x6a/0x32c mm/kasan/report.c:351
> __kasan_report.cold+0x1a/0x33 mm/kasan/report.c:482
> kasan_report+0xe/0x12 mm/kasan/common.c:612
> memcmp+0xa6/0xb0 lib/string.c:904
> memcmp include/linux/string.h:400 [inline]
> descriptors_changed drivers/usb/core/hub.c:5579 [inline]
> usb_reset_and_verify_device+0x564/0x1300 drivers/usb/core/hub.c:5729

Diagnostic patch.

#syz test: https://github.com/google/kasan.git eea39f24

Index: usb-devel/drivers/usb/core/hub.c
===================================================================
--- usb-devel.orig/drivers/usb/core/hub.c
+++ usb-devel/drivers/usb/core/hub.c
@@ -5721,6 +5721,13 @@ static int usb_reset_and_verify_device(s
if (ret < 0)
goto re_enumerate;

+ if (bos)
+ dev_info(&udev->dev, "Old BOS %p Len 0x%x\n",
+ bos, le16_to_cpu(bos->desc->wTotalLength));
+ if (udev->bos)
+ dev_info(&udev->dev, "New BOS %p Len 0x%x\n",
+ udev->bos, le16_to_cpu(udev->bos->desc->wTotalLength));
+
/* Device might have changed firmware (DFU or similar) */
if (descriptors_changed(udev, &descriptor, bos)) {
dev_info(&udev->dev, "device firmware changed\n");
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