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Date:   Mon, 16 Sep 2019 16:51:42 -0400 (EDT)
From:   Alan Stern <stern@rowland.harvard.edu>
To:     syzbot <syzbot+7fa38a608b1075dfd634@syzkaller.appspotmail.com>
cc:     andreyknvl@google.com, <gregkh@linuxfoundation.org>,
        <kai.heng.feng@canonical.com>, <linux-kernel@vger.kernel.org>,
        <linux-usb@vger.kernel.org>, <mans@mansr.com>, <oneukum@suse.com>,
        <syzkaller-bugs@googlegroups.com>
Subject: Re: general protection fault in usb_set_interface
In-Reply-To: <000000000000c2531f0592ab96fb@google.com>
Message-ID: <Pine.LNX.4.44L0.1909161650440.1489-100000@iolanthe.rowland.org>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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=158b66f1600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=5c6633fa4ed00be5
> dashboard link: https://syzkaller.appspot.com/bug?extid=7fa38a608b1075dfd634
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14f57db9600000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=127b61a5600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+7fa38a608b1075dfd634@syzkaller.appspotmail.com
> 
> usb 3-1: usbvision_write_reg: failed: error -2
> usbvision_set_audio: can't write iopin register for audio switching
> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] SMP KASAN
> CPU: 1 PID: 1955 Comm: v4l_id Not tainted 5.3.0-rc7+ #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> Google 01/01/2011
> RIP: 0010:usb_set_interface+0x34/0xa50 drivers/usb/core/message.c:1362
> Code: fc 55 53 48 83 ec 40 89 54 24 18 89 74 24 10 e8 22 1c ef fd 49 8d 7c  
> 24 48 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
> 85 fb 08 00 00 49 8b 44 24 48 49 8d 7c 24 18 48 89
> RSP: 0018:ffff8881cb19fd50 EFLAGS: 00010206
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 0000000000000009 RSI: ffffffff834ebe7e RDI: 0000000000000048
> RBP: ffff8881cb8e4200 R08: ffffffff88d21878 R09: ffffed103971cb43
> R10: ffff8881cb19fdc8 R11: ffff8881cb8e5a17 R12: 0000000000000000
> R13: ffff8881cb8e5a10 R14: ffff8881cb8e4cc8 R15: ffff8881cb8e5178
> FS:  00007f4f60b6d700(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f4f6060c330 CR3: 00000001cc3a8000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   usbvision_radio_close+0x105/0x250  
> drivers/media/usb/usbvision/usbvision-video.c:1114
>   v4l2_release+0x2e7/0x390 drivers/media/v4l2-core/v4l2-dev.c:455
>   __fput+0x2d7/0x840 fs/file_table.c:280
>   task_work_run+0x13f/0x1c0 kernel/task_work.c:113
>   tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>   exit_to_usermode_loop+0x1d2/0x200 arch/x86/entry/common.c:163
>   prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
>   syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
>   do_syscall_64+0x45f/0x580 arch/x86/entry/common.c:299
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x7f4f6069b2b0
> Code: 40 75 0b 31 c0 48 83 c4 08 e9 0c ff ff ff 48 8d 3d c5 32 08 00 e8 c0  
> 07 02 00 83 3d 45 a3 2b 00 00 75 10 b8 03 00 00 00 0f 05 <48> 3d 01 f0 ff  
> ff 73 31 c3 48 83 ec 08 e8 ce 8a 01 00 48 89 04 24
> RSP: 002b:00007ffde2d50ee8 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
> RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00007f4f6069b2b0
> RDX: 00007f4f60951df0 RSI: 0000000000000001 RDI: 0000000000000003
> RBP: 0000000000000000 R08: 00007f4f60951df0 R09: 000000000000000a
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000400884
> R13: 00007ffde2d51040 R14: 0000000000000000 R15: 0000000000000000
> Modules linked in:
> ---[ end trace 62bd2b7512ab49ee ]---
> RIP: 0010:usb_set_interface+0x34/0xa50 drivers/usb/core/message.c:1362
> Code: fc 55 53 48 83 ec 40 89 54 24 18 89 74 24 10 e8 22 1c ef fd 49 8d 7c  
> 24 48 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
> 85 fb 08 00 00 49 8b 44 24 48 49 8d 7c 24 18 48 89
> RSP: 0018:ffff8881cb19fd50 EFLAGS: 00010206
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 0000000000000009 RSI: ffffffff834ebe7e RDI: 0000000000000048
> RBP: ffff8881cb8e4200 R08: ffffffff88d21878 R09: ffffed103971cb43
> R10: ffff8881cb19fdc8 R11: ffff8881cb8e5a17 R12: 0000000000000000
> R13: ffff8881cb8e5a10 R14: ffff8881cb8e4cc8 R15: ffff8881cb8e5178
> FS:  00007f4f60b6d700(0000) GS:ffff8881db300000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f4f6060c330 CR3: 00000001cc3a8000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> 
> 
> ---
> 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

Use-after-free bug.

Alan Stern

#syz test: https://github.com/google/kasan.git f0df5c1b

 drivers/media/usb/usbvision/usbvision-video.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: usb-devel/drivers/media/usb/usbvision/usbvision-video.c
===================================================================
--- usb-devel.orig/drivers/media/usb/usbvision/usbvision-video.c
+++ usb-devel/drivers/media/usb/usbvision/usbvision-video.c
@@ -1111,7 +1111,8 @@ static int usbvision_radio_close(struct
 	mutex_lock(&usbvision->v4l2_lock);
 	/* Set packet size to 0 */
 	usbvision->iface_alt = 0;
-	usb_set_interface(usbvision->dev, usbvision->iface,
+	if (usbvision->dev)
+		usb_set_interface(usbvision->dev, usbvision->iface,
 				    usbvision->iface_alt);
 
 	usbvision_audio_off(usbvision);