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Message-ID: <Pine.LNX.4.44L0.1910241053590.1676-100000@iolanthe.rowland.org>
Date: Thu, 24 Oct 2019 11:04:26 -0400 (EDT)
From: Alan Stern <stern@...land.harvard.edu>
To: syzbot <syzbot+8ab8bf161038a8768553@...kaller.appspotmail.com>
cc: Jacky.Cao@...y.com, <andreyknvl@...gle.com>, <balbi@...nel.org>,
<chunfeng.yun@...iatek.com>, <gregkh@...uxfoundation.org>,
<linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>,
<syzkaller-bugs@...glegroups.com>
Subject: Re: divide error in dummy_timer
On Thu, 24 Oct 2019, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit: 22be26f7 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=11e2fda7600000
> kernel config: https://syzkaller.appspot.com/x/.config?x=5fe29bc39eff9627
> dashboard link: https://syzkaller.appspot.com/bug?extid=8ab8bf161038a8768553
> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14f664e4e00000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14674000e00000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+8ab8bf161038a8768553@...kaller.appspotmail.com
>
> divide error: 0000 [#1] SMP KASAN
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.4.0-rc3+ #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:transfer drivers/usb/gadget/udc/dummy_hcd.c:1426 [inline]
> RIP: 0010:dummy_timer+0xad5/0x2fa2 drivers/usb/gadget/udc/dummy_hcd.c:1950
> Code: 0f 84 f5 fd ff ff e8 8a 55 ab fd 89 de 44 89 e7 e8 70 56 ab fd 41 39
> dc 0f 82 b0 08 00 00 e8 72 55 ab fd 44 89 e0 31 d2 31 ff <f7> f3 89 d6 89
> 94 24 c0 00 00 00 e8 cb 56 ab fd 8b 94 24 c0 00 00
> RSP: 0018:ffff8881db209b20 EFLAGS: 00010046
> RAX: 0000000000000040 RBX: 0000000000000000 RCX: ffffffff8392c330
> RDX: 0000000000000000 RSI: ffffffff8392c33e RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffff86c2b200 R09: ffffed103b641353
> R10: ffffed103b641352 R11: 0000000000000003 R12: 0000000000000040
> R13: ffff8881d58c0000 R14: dffffc0000000000 R15: ffff8881d78d5a00
> FS: 0000000000000000(0000) GS:ffff8881db200000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fb771a61000 CR3: 00000001d2295000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
> <IRQ>
> call_timer_fn+0x179/0x650 kernel/time/timer.c:1404
> expire_timers kernel/time/timer.c:1449 [inline]
> __run_timers kernel/time/timer.c:1773 [inline]
> __run_timers kernel/time/timer.c:1740 [inline]
> run_timer_softirq+0x5e3/0x1490 kernel/time/timer.c:1786
> __do_softirq+0x221/0x912 kernel/softirq.c:292
> invoke_softirq kernel/softirq.c:373 [inline]
> irq_exit+0x178/0x1a0 kernel/softirq.c:413
> exiting_irq arch/x86/include/asm/apic.h:536 [inline]
> smp_apic_timer_interrupt+0x12f/0x500 arch/x86/kernel/apic/apic.c:1137
> apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830
> </IRQ>
> RIP: 0010:default_idle+0x28/0x2e0 arch/x86/kernel/process.c:581
> Code: 90 90 41 56 41 55 65 44 8b 2d f4 00 92 7a 41 54 55 53 0f 1f 44 00 00
> e8 c6 b2 d3 fb e9 07 00 00 00 0f 00 2d ea a5 52 00 fb f4 <65> 44 8b 2d d0
> 00 92 7a 0f 1f 44 00 00 5b 5d 41 5c 41 5d 41 5e c3
> RSP: 0018:ffffffff86c07da8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
> RAX: 0000000000000007 RBX: ffffffff86c2b200 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffffffff86c2ba4c
> RBP: fffffbfff0d85640 R08: ffffffff86c2b200 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> cpuidle_idle_call kernel/sched/idle.c:154 [inline]
> do_idle+0x3b6/0x500 kernel/sched/idle.c:263
> cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:355
> start_kernel+0x82a/0x864 init/main.c:784
> secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241
> Modules linked in:
> ---[ end trace 02e2d9c7c53d85a5 ]---
> RIP: 0010:transfer drivers/usb/gadget/udc/dummy_hcd.c:1426 [inline]
> RIP: 0010:dummy_timer+0xad5/0x2fa2 drivers/usb/gadget/udc/dummy_hcd.c:1950
> Code: 0f 84 f5 fd ff ff e8 8a 55 ab fd 89 de 44 89 e7 e8 70 56 ab fd 41 39
> dc 0f 82 b0 08 00 00 e8 72 55 ab fd 44 89 e0 31 d2 31 ff <f7> f3 89 d6 89
> 94 24 c0 00 00 00 e8 cb 56 ab fd 8b 94 24 c0 00 00
> RSP: 0018:ffff8881db209b20 EFLAGS: 00010046
> RAX: 0000000000000040 RBX: 0000000000000000 RCX: ffffffff8392c330
> RDX: 0000000000000000 RSI: ffffffff8392c33e RDI: 0000000000000000
> RBP: 0000000000000000 R08: ffffffff86c2b200 R09: ffffed103b641353
> R10: ffffed103b641352 R11: 0000000000000003 R12: 0000000000000040
> R13: ffff8881d58c0000 R14: dffffc0000000000 R15: ffff8881d78d5a00
> FS: 0000000000000000(0000) GS:ffff8881db200000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fb771a61000 CR3: 00000001d2295000 CR4: 00000000001406f0
> 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@...glegroups.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
Is this really the sort of thing we need to catch? It isn't a bug in
any existing kernel code, as far as I know. Maybe only gadgetfs and
configfs need to worry about it.
Alan Stern
#syz test: https://github.com/google/kasan.git 22be26f7
drivers/usb/gadget/udc/dummy_hcd.c | 2 ++
1 file changed, 2 insertions(+)
Index: usb-devel/drivers/usb/gadget/udc/dummy_hcd.c
===================================================================
--- usb-devel.orig/drivers/usb/gadget/udc/dummy_hcd.c
+++ usb-devel/drivers/usb/gadget/udc/dummy_hcd.c
@@ -522,6 +522,8 @@ static int dummy_enable(struct usb_ep *_
* For SS devices the wMaxPacketSize is limited by 1024.
*/
max = usb_endpoint_maxp(desc);
+ if (max == 0)
+ return -EINVAL;
/* drivers must not request bad settings, since lower levels
* (hardware or its drivers) may not check. some endpoints
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