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Date:   Sat, 9 May 2020 09:45:07 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     syzbot <syzbot+353be47c9ce21b68b7ed@...kaller.appspotmail.com>,
        bp@...en8.de, dave.hansen@...ux.intel.com,
        dmitry.torokhov@...il.com, ebiederm@...ssion.com, hpa@...or.com,
        jeremy.linton@....com, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, luto@...nel.org, mingo@...hat.com,
        peterz@...radead.org, stern@...land.harvard.edu,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de, x86@...nel.org
Subject: Re: WARNING in memtype_reserve

On Sat, May 09, 2020 at 12:20:14AM -0700, 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@....com>
> 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@...kaller.appspotmail.com
> 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..

So should memtype_reserve() not do a WARN if given invalid parameters as
it can be triggered by userspace requests?

A normal "invalid request" debug line is probably all that is needed,
right?

thanks,

greg k-h

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