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Date:   Tue, 17 Sep 2019 14:24:51 -0400 (EDT)
From:   Alan Stern <stern@rowland.harvard.edu>
To:     syzbot <syzbot+403741a091bf41d4ae79@syzkaller.appspotmail.com>
cc:     andreyknvl@google.com, <benjamin.tissoires@redhat.com>,
        <jikos@kernel.org>, <linux-input@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-usb@vger.kernel.org>,
        <syzkaller-bugs@googlegroups.com>
Subject: Re: KASAN: slab-out-of-bounds Write in ga_probe
In-Reply-To: <000000000000cd1def0592ab9697@google.com>
Message-ID: <Pine.LNX.4.44L0.1909171423360.1590-100000@iolanthe.rowland.org>
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Sender: linux-kernel-owner@vger.kernel.org
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On Mon, 16 Sep 2019, syzbot wrote:

> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    f0df5c1b 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=14045831600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
> dashboard link: https://syzkaller.appspot.com/bug?extid=403741a091bf41d4ae79
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13c1e62d600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=166a3a95600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+403741a091bf41d4ae79@syzkaller.appspotmail.com
> 
> usb 1-1: config 0 interface 0 altsetting 0 has 1 endpoint descriptor,  
> different from the interface descriptor's value: 9
> usb 1-1: New USB device found, idVendor=0e8f, idProduct=0012, bcdDevice=  
> 0.00
> usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
> usb 1-1: config 0 descriptor??
> greenasia 0003:0E8F:0012.0001: unknown main item tag 0x0
> greenasia 0003:0E8F:0012.0001: hidraw0: USB HID v0.00 Device [HID  
> 0e8f:0012] on usb-dummy_hcd.0-1/input0
> ==================================================================
> BUG: KASAN: slab-out-of-bounds in set_bit  
> include/asm-generic/bitops-instrumented.h:28 [inline]
> BUG: KASAN: slab-out-of-bounds in gaff_init drivers/hid/hid-gaff.c:97  
> [inline]
> BUG: KASAN: slab-out-of-bounds in ga_probe+0x1fd/0x6f0  
> drivers/hid/hid-gaff.c:146
> Write of size 8 at addr ffff8881d9acafc0 by task kworker/1:1/78
> 
> CPU: 1 PID: 78 Comm: kworker/1:1 Not tainted 5.3.0-rc7+ #0
> 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:618
>   check_memory_region_inline mm/kasan/generic.c:185 [inline]
>   check_memory_region+0x128/0x190 mm/kasan/generic.c:192
>   set_bit include/asm-generic/bitops-instrumented.h:28 [inline]
>   gaff_init drivers/hid/hid-gaff.c:97 [inline]
>   ga_probe+0x1fd/0x6f0 drivers/hid/hid-gaff.c:146
>   hid_device_probe+0x2be/0x3f0 drivers/hid/hid-core.c:2209
>   really_probe+0x281/0x6d0 drivers/base/dd.c:548
>   driver_probe_device+0x101/0x1b0 drivers/base/dd.c:721
>   __device_attach_driver+0x
> 
> 
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
> 
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches

The driver assumes that the device contains an input.

Alan Stern

https://github.com/google/kasan.git f0df5c1b

 drivers/hid/hid-gaff.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

Index: usb-devel/drivers/hid/hid-gaff.c
===================================================================
--- usb-devel.orig/drivers/hid/hid-gaff.c
+++ usb-devel/drivers/hid/hid-gaff.c
@@ -64,14 +64,20 @@ static int gaff_init(struct hid_device *
 {
 	struct gaff_device *gaff;
 	struct hid_report *report;
-	struct hid_input *hidinput = list_entry(hid->inputs.next,
-						struct hid_input, list);
+	struct hid_input *hidinput;
 	struct list_head *report_list =
 			&hid->report_enum[HID_OUTPUT_REPORT].report_list;
 	struct list_head *report_ptr = report_list;
-	struct input_dev *dev = hidinput->input;
+	struct input_dev *dev;
 	int error;
 
+	if (list_empty(&hid->inputs)) {
+		hid_err(hid, "no inputs found\n");
+		return -ENODEV;
+	}
+	hidinput = list_entry(hid->inputs.next, struct hid_input, list);
+	dev = hidinput->input;
+
 	if (list_empty(report_list)) {
 		hid_err(hid, "no output reports found\n");
 		return -ENODEV;