linux-kernel - Re: WARNING in kmalloc

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Message-ID: <CACT4Y+aE-Q-PeUaY99d2UbK4BHnf18OoV0MBXyOXzXttf1=nYw@mail.gmail.com>
Date:   Mon, 4 Dec 2017 09:18:05 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Eric Biggers <ebiggers3@...il.com>,
        syzbot 
        <bot+2797c18fc195e3e240c3c3e7837a14130e157fb0@...kaller.appspotmail.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>, dave.jiang@...el.com,
        LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs@...glegroups.com, Al Viro <viro@...iv.linux.org.uk>,
        linux-block@...r.kernel.org
Subject: Re: WARNING in kmalloc_slab (3)

On Mon, Dec 4, 2017 at 9:14 AM, Dan Carpenter <dan.carpenter@...cle.com> wrote:
> On Sun, Dec 03, 2017 at 12:16:08PM -0800, Eric Biggers wrote:
>> Looks like BLKTRACESETUP doesn't limit the '.buf_nr' parameter, allowing anyone
>> who can open a block device to cause an extremely large kmalloc.  Here's a
>> simplified reproducer:
>>
>
> There are lots of places which allow people to allocate as much as they
> want.  With Syzcaller, you might want to just hard code a __GFP_NOWARN
> in to disable it.

Hi,

Hard code it where?

User-controllable allocation are supposed to use __GFP_NOWARN.