Re: WARNING in memtype_reserve

[Jeremy Linton]

Hi,

On 5/9/20 2:20 AM, syzbot wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    d5eeab8d Merge tag 'scsi-fixes' of git://git.kernel.org/pu..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15093632100000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=b0212dbee046bc1f
> dashboard link: https://syzkaller.appspot.com/bug?extid=353be47c9ce21b68b7ed
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> userspace arch: i386
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=168ee02c100000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=119f3788100000
>
> The bug was bisected to:
>
> commit 2bef9aed6f0e22391c8d4570749b1acc9bc3981e
> Author: Jeremy Linton <jeremy.linton@xxxxxxx>
> Date:   Mon May 4 20:13:48 2020 +0000
>
>      usb: usbfs: correct kernel->user page attribute mismatch
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1701f168100000
> final crash:    https://syzkaller.appspot.com/x/report.txt?x=1481f168100000
> console output: https://syzkaller.appspot.com/x/log.txt?x=1081f168100000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+353be47c9ce21b68b7ed@xxxxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 2bef9aed6f0e ("usb: usbfs: correct kernel->user page attribute mismatch")
>
> ------------[ cut here ]------------
> memtype_reserve failed: [mem 0xffffffffff000-0x00008fff], req write-back
> WARNING: CPU: 1 PID: 7025 at arch/x86/mm/pat/memtype.c:589 memtype_reserve+0x69f/0x820 arch/x86/mm/pat/memtype.c:589
> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 1 PID: 7025 Comm: syz-executor254 Not tainted 5.7.0-rc4-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x188/0x20d lib/dump_stack.c:118
>   panic+0x2e3/0x75c kernel/panic.c:221
>   __warn.cold+0x2f/0x35 kernel/panic.c:582
>   report_bug+0x27b/0x2f0 lib/bug.c:195
>   fixup_bug arch/x86/kernel/traps.c:175 [inline]
>   fixup_bug arch/x86/kernel/traps.c:170 [inline]
>   do_error_trap+0x12b/0x220 arch/x86/kernel/traps.c:267
>   do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286
>   invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
> RIP: 0010:memtype_reserve+0x69f/0x820 arch/x86/mm/pat/memtype.c:589
> Code: 48 8b 2c ed c0 00 29 88 e8 ae ad 3e 00 48 8d 4b ff 49 89 e8 4c 89 e2 48 c7 c6 20 01 29 88 48 c7 c7 80 f9 28 88 e8 79 e8 0f 00 <0f> 0b 41 bf ea ff ff ff e9 03 fc ff ff 41 bf ea ff ff ff e9 f8 fb
> RSP: 0018:ffffc900015e7790 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: 0000000000009000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff815ce181 RDI: fffff520002bcee4
> RBP: ffffffff8828ff40 R08: ffff888097ce85c0 R09: ffffed1015ce45f1
> R10: ffff8880ae722f83 R11: ffffed1015ce45f0 R12: 000ffffffffff000
> R13: 1ffff920002bcef8 R14: dffffc0000000000 R15: 0000000000000000
>   reserve_pfn_range+0x173/0x470 arch/x86/mm/pat/memtype.c:941
>   track_pfn_remap+0x18b/0x280 arch/x86/mm/pat/memtype.c:1033
>   remap_pfn_range+0x202/0xbf0 mm/memory.c:2130
>   dma_direct_mmap+0x197/0x260 kernel/dma/direct.c:453
>   dma_mmap_attrs+0xfe/0x150 kernel/dma/mapping.c:237
>   usbdev_mmap+0x3ae/0x730 drivers/usb/core/devio.c:254
>   call_mmap include/linux/fs.h:1912 [inline]
>   mmap_region+0xafb/0x1540 mm/mmap.c:1772
>   do_mmap+0x849/0x1160 mm/mmap.c:1545
>   do_mmap_pgoff include/linux/mm.h:2553 [inline]
>   vm_mmap_pgoff+0x197/0x200 mm/util.c:506
>   ksys_mmap_pgoff+0x457/0x5b0 mm/mmap.c:1595
>   do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
>   do_fast_syscall_32+0x270/0xe90 arch/x86/entry/common.c:396
>   entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
>
>
> ---
> 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@xxxxxxxxxxxxxxxxx
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> For information about bisection process see: https://goo.gl/tpsmEJ#bisection
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches

Adding a range check in dma_direct_mmap() looks like a fine fix. I'm 
curious how the mapping attribute changed though. I expected that would 
be rare on x86 (ISA devices/etc).

What is the GCE USB controller here? Its not the same as the virtual 
qemu/pci/xhci right?