From: Sumit Semwal <sumit.semwal@linaro.org>
To: guangming.cao@mediatek.com
Cc: christian.koenig@amd.com, brian.starkey@arm.com,
benjamin.gaignard@linaro.org, bo.song@mediatek.com,
dri-devel@lists.freedesktop.org, jianjiao.zeng@mediatek.com,
john.stultz@linaro.org, labbott@redhat.com,
libo.kang@mediatek.com, linaro-mm-sig@lists.linaro.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
linux-mediatek@lists.infradead.org, lmark@codeaurora.org,
matthias.bgg@gmail.com, mingyuan.ma@mediatek.com,
wsd_upstream@mediatek.com, yf.wang@mediatek.com
Subject: Re: [PATCH v2] dma-buf: dma-heap: Add a size check for allocation
Date: Thu, 13 Jan 2022 16:20:36 +0530 [thread overview]
Message-ID: <CAO_48GF=ttKqSOm9GRoA3Mq+-RQOtRjWp449XPcz-wH=kjaTjw@mail.gmail.com> (raw)
In-Reply-To: <20220105063643.119874-1-guangming.cao@mediatek.com>
Hello Guangming,
On Wed, 5 Jan 2022 at 12:05, <guangming.cao@mediatek.com> wrote:
>
> From: Guangming.Cao <guangming.cao@mediatek.com>
>
> On Tue, 2022-01-04 at 08:47 +0100, Christian K鰊ig wrote:
> > Am 03.01.22 um 19:57 schrieb John Stultz:
> > > On Mon, Dec 27, 2021 at 1:52 AM <guangming.cao@mediatek.com> wrote:
> > > > From: Guangming <Guangming.Cao@mediatek.com>
> > > >
> > >
> > > Thanks for submitting this!
> > >
> > > > Add a size check for allcation since the allocation size is
> > >
> > > nit: "allocation" above.
> > >
> > > > always less than the total DRAM size.
> > >
> > > In general, it might be good to add more context to the commit
> > > message
> > > to better answer *why* this change is needed rather than what the
> > > change is doing. ie: What negative thing happens without this
> > > change?
> > > And so how does this change avoid or improve things?
> >
> > Completely agree, just one little addition: Could you also add this
> > why
> > as comment to the code?
> >
> > When we stumble over this five years from now it is absolutely not
> > obvious why we do this.
> >
> > Thanks,
> > Christian.
> >
> Thanks for your reply!
> I will update the related reason in the patch later.
>
> The reason for adding this check is that we met a case that the user
> sent an invalid size(It seems it's a negative value, MSB is 0xff, it's
> larger than DRAM size after convert it to size_t) to dma-heap to alloc
> memory, and this allocation was running on a process(such as "gralloc"
> on Android device) can't be killed by OOM flow, and we also couldn't
> find the related dmabuf in "dma_buf_debug_show" because the related
> dmabuf was not exported yet since the allocation is still on going.
>
> Since this invalid argument case can be prevented at dma-heap side, so,
> I added this size check, and moreover, to let debug it easily, I also
> added logs when size is bigger than a threshold we set in mtk system
> heap.
> If you think that print logs in dma-heap framework is better, I will
> update it in next version.
>
> If you have better solution(such as dump the size under allocating
> in "dma_buf_debug_show", which maybe need add global variable to record
> it), please kindly let me know.
Thank you for the patch!
I think just adding the reasoning above as the commit message and a
comment in the code should be enough for now; the debug parts may be
easy to add in case someone runs into issues.
> Thanks :)
> Guangming
Best,
Sumit.
>
> > >
> > >
> > > > Signed-off-by: Guangming <Guangming.Cao@mediatek.com>
> > > > Signed-off-by: jianjiao zeng <jianjiao.zeng@mediatek.com>
> > > > ---
> > > > v2: 1. update size limitation as total_dram page size.
> > > > 2. update commit message
> > > > ---
> > > > drivers/dma-buf/dma-heap.c | 2 ++
> > > > 1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-
> > > > heap.c
> > > > index 56bf5ad01ad5..e39d2be98d69 100644
> > > > --- a/drivers/dma-buf/dma-heap.c
> > > > +++ b/drivers/dma-buf/dma-heap.c
> > > > @@ -55,6 +55,8 @@ static int dma_heap_buffer_alloc(struct
> > > > dma_heap *heap, size_t len,
> > > > struct dma_buf *dmabuf;
> > > > int fd;
> > > >
> > > > + if (len / PAGE_SIZE > totalram_pages())
> > > > + return -EINVAL;
> > >
> > > This seems sane. I know ION used to have some 1/2 of memory cap to
> > > avoid unnecessary memory pressure on crazy allocations.
> > >
> > > Could you send again with an improved commit message?
> > >
> > > thanks
> > > -john
> >
> >
--
Thanks and regards,
Sumit Semwal (he / him)
Tech Lead - LCG, Vertical Technologies
Linaro.org │ Open source software for ARM SoCs
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next prev parent reply other threads:[~2022-01-13 10:51 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-17 9:41 [PATCH] dma-buf: dma-heap: Add a size limitation for allocation guangming.cao
2021-12-27 9:51 ` [PATCH v2] dma-buf: dma-heap: Add a size check " guangming.cao
2022-01-03 18:57 ` John Stultz
2022-01-04 7:47 ` Christian König
2022-01-04 8:44 ` Guangming.Cao
2022-01-05 6:36 ` guangming.cao
2022-01-13 10:50 ` Sumit Semwal [this message]
2022-01-13 12:34 ` [PATCH v3] " guangming.cao
2022-01-13 12:57 ` Ruhl, Michael J
2022-01-13 13:00 ` Ruhl, Michael J
2022-01-13 13:05 ` Christian König
2022-01-13 23:26 ` John Stultz
2022-01-14 7:16 ` Christian König
2022-01-14 12:05 ` Guangming.Cao
2022-01-15 1:17 ` John Stultz
2022-01-19 9:59 ` Guangming.Cao
2022-01-19 20:37 ` John Stultz
2022-01-20 3:34 ` [PATCH v4] dma-buf: system_heap: " guangming.cao
2022-01-20 3:48 ` John Stultz
2022-01-20 7:08 ` [PATCH v5] " guangming.cao
2022-01-20 8:27 ` Christian König
2022-01-20 8:52 ` [PATCH v6] " guangming.cao
2022-01-20 10:00 ` [PATCH v6 RESEND] " guangming.cao
2022-01-20 10:22 ` Christian König
2021-12-27 9:47 [PATCH v2] dma-buf: dma-heap: " guangming.cao
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