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From: Alan Stern <stern@rowland.harvard.edu>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	syzbot <syzbot+353be47c9ce21b68b7ed@syzkaller.appspotmail.com>,
	<bp@alien8.de>, <dave.hansen@linux.intel.com>,
	<dmitry.torokhov@gmail.com>, <ebiederm@xmission.com>,
	<hpa@zytor.com>, <jeremy.linton@arm.com>,
	<linux-kernel@vger.kernel.org>, <linux-usb@vger.kernel.org>,
	<luto@kernel.org>, <mingo@redhat.com>, <peterz@infradead.org>,
	<syzkaller-bugs@googlegroups.com>, <x86@kernel.org>
Subject: Re: WARNING in memtype_reserve
Date: Sat, 9 May 2020 09:41:55 -0400 (EDT)	[thread overview]
Message-ID: <Pine.LNX.4.44L0.2005090939210.4307-100000@netrider.rowland.org> (raw)
In-Reply-To: <87wo5l4ecm.fsf@nanos.tec.linutronix.de>

On Sat, 9 May 2020, Thomas Gleixner wrote:

> Greg KH <gregkh@linuxfoundation.org> writes:
> > On Sat, May 09, 2020 at 12:20:14AM -0700, syzbot wrote:
> >> 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
> >
> > 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?
> 
> I disagree. The callsite espcially if user space triggerable should not
> attempt to ask for a reservation where start > end:
> 
>   >> memtype_reserve failed: [mem 0xffffffffff000-0x00008fff], req write-back
> 
> The real question is which part of the call chain is responsible for
> this. That needs to be fixed.

What about all the other ways in which a reservation request could be
invalid?  The MM core already checks for these; what point is there in
duplicating these checks in many places higher up the call chain?

Alan Stern


  reply	other threads:[~2020-05-09 13:41 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-09  7:20 WARNING in memtype_reserve syzbot
2020-05-09  7:45 ` Greg KH
2020-05-09 10:00   ` Thomas Gleixner
2020-05-09 13:41     ` Alan Stern [this message]
2020-05-13 16:21       ` Thomas Gleixner
2020-05-13 12:44     ` Greg KH
2020-05-13 16:22       ` Thomas Gleixner
2020-05-13 16:55         ` Greg KH
     [not found]         ` <20200514035458.14760-1-hdanton@sina.com>
2020-05-14  6:14           ` Christoph Hellwig
2020-05-14  6:19             ` Dmitry Vyukov
2020-05-14  6:27             ` Validating dma_mmap_coherent() parameters before calling (was Re: WARNING in memtype_reserve) Greg KH
2020-05-14  6:31               ` Christoph Hellwig
2020-05-14  7:46                 ` Greg KH
2020-05-14 11:17                   ` Jeremy Linton
2020-05-14 11:22                     ` Greg KH
2020-05-14 11:10                 ` Jeremy Linton
2020-05-14 11:14                   ` Christoph Hellwig
2020-05-14 11:16                     ` Jeremy Linton
2020-05-14  9:08           ` WARNING in memtype_reserve syzbot
2020-05-09 17:42 ` Jeremy Linton
     [not found] ` <20200509154728.1548-1-hdanton@sina.com>
2020-05-13 12:41   ` Greg KH
2020-05-14  9:20 ` Greg KH
2020-05-14 10:44   ` syzbot

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