From: Christopher Lameter <cl@linux.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>,
syzbot+87829a10073277282ad1@syzkaller.appspotmail.com,
Pekka Enberg <penberg@kernel.org>,
"linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Henrik Rydberg <rydberg@bitmath.org>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: WARNING: kmalloc bug in input_mt_init_slots
Date: Mon, 24 Sep 2018 15:55:04 +0000 [thread overview]
Message-ID: <010001660c4a8bbe-91200766-00df-48bd-bc60-a03da2ccdb7d-000000@email.amazonses.com> (raw)
In-Reply-To: <CACT4Y+ayX8vzd2JPrLeFhf3K_Quf4x6SDtmtkNJuwNLyOh67tQ@mail.gmail.com>
On Mon, 24 Sep 2018, Dmitry Vyukov wrote:
> On Mon, Sep 24, 2018 at 5:08 PM, Christopher Lameter <cl@linux.com> wrote:
> > On Sun, 23 Sep 2018, Dmitry Vyukov wrote:
> >
> >> What was the motivation behind that WARNING about large allocations in
> >> kmalloc? Why do we want to know about them? Is the general policy that
> >> kmalloc calls with potentially large size requests need to use NOWARN?
> >> If this WARNING still considered useful? Or we should change it to
> >> pr_err?
> >
> > In general large allocs should be satisfied by the page allocator. The
> > slab allocators are used for allocating and managing small objects. The
> > page allocator has mechanisms to deal with large objects (compound pages,
> > multiple page sized allocs etc).
>
> I am asking more about the status of this warning. If it fires in
> input_mt_init_slots(), does it mean that input_mt_init_slots() needs
> to be fixed? If not, then we need to change this warning to something
> else.
Hmmm.. kmalloc falls back to the page allocator already?
See
static __always_inline void *kmalloc(size_t size, gfp_t flags)
{
if (__builtin_constant_p(size)) {
if (size > KMALLOC_MAX_CACHE_SIZE)
return kmalloc_large(size, flags);
Note that this uses KMALLOC_MAX_CACHE_SIZE which should be smaller than
KMALLOC_MAX_SIZE.
How large is the allocation? AFACIT nRequests larger than KMALLOC_MAX_SIZE
are larger than the maximum allowed by the page allocator. Thus the warning
and the NULL return.
next prev parent reply other threads:[~2018-09-24 15:55 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-21 17:24 WARNING: kmalloc bug in input_mt_init_slots syzbot
2018-09-21 17:52 ` Dmitry Torokhov
2018-09-23 16:33 ` Dmitry Vyukov
2018-09-24 15:08 ` Christopher Lameter
2018-09-24 15:18 ` Dmitry Vyukov
2018-09-24 15:55 ` Christopher Lameter [this message]
2018-09-24 18:41 ` Dmitry Torokhov
2018-09-25 7:39 ` Dmitry Vyukov
2018-09-25 14:04 ` Christopher Lameter
2018-09-27 13:07 ` Dmitry Vyukov
2018-09-27 14:16 ` Christopher Lameter
2018-09-27 14:28 ` Dmitry Vyukov
2018-09-27 15:22 ` Christopher Lameter
2018-09-27 15:29 ` Dmitry Vyukov
2018-09-27 15:47 ` Christopher Lameter
2018-09-27 14:35 ` Matthew Wilcox
2018-10-17 0:09 ` Dmitry Torokhov
2018-10-17 15:35 ` Christopher Lameter
2018-10-17 15:43 ` Dmitry Torokhov
2018-10-17 15:53 ` Christopher Lameter
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