Re: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation

[Christian König]

Am 13.01.22 um 14:00 schrieb Ruhl, Michael J:
> > -----Original Message-----
> > From: dri-devel <dri-devel-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of
> > Ruhl, Michael J
> > Sent: Thursday, January 13, 2022 7:58 AM
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> > Cc: jianjiao.zeng@xxxxxxxxxxxx; lmark@xxxxxxxxxxxxxx;
> > wsd_upstream@xxxxxxxxxxxx; christian.koenig@xxxxxxx; linux-
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> > mediatek@xxxxxxxxxxxxxxxxxxx; libo.kang@xxxxxxxxxxxx;
> > benjamin.gaignard@xxxxxxxxxx; bo.song@xxxxxxxxxxxx;
> > matthias.bgg@xxxxxxxxx; labbott@xxxxxxxxxx;
> > mingyuan.ma@xxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> > media@xxxxxxxxxxxxxxx
> > Subject: RE: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation
> >
> >
> > > -----Original Message-----
> > > From: dri-devel <dri-devel-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of
> > > guangming.cao@xxxxxxxxxxxx
> > > Sent: Thursday, January 13, 2022 7:34 AM
> > > To: sumit.semwal@xxxxxxxxxx
> > > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; mingyuan.ma@xxxxxxxxxxxx;
> > > Guangming <Guangming.Cao@xxxxxxxxxxxx>;
> > > wsd_upstream@xxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; dri-
> > > devel@xxxxxxxxxxxxxxxxxxxxx; linaro-mm-sig@xxxxxxxxxxxxxxxx;
> > > yf.wang@xxxxxxxxxxxx; libo.kang@xxxxxxxxxxxx;
> > > benjamin.gaignard@xxxxxxxxxx; bo.song@xxxxxxxxxxxx;
> > > matthias.bgg@xxxxxxxxx; linux-mediatek@xxxxxxxxxxxxxxxxxxx;
> > > lmark@xxxxxxxxxxxxxx; labbott@xxxxxxxxxx; christian.koenig@xxxxxxx;
> > > jianjiao.zeng@xxxxxxxxxxxx; linux-media@xxxxxxxxxxxxxxx
> > > Subject: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation
> > >
> > > From: Guangming <Guangming.Cao@xxxxxxxxxxxx>
> > >
> > > Add a size check for allocation since the allocation size is
> > > always less than the total DRAM size.
> > >
> > > Without this check, once the invalid size allocation runs on a process that
> > > can't be killed by OOM flow(such as "gralloc" on Android devices), it will
> > > cause a kernel exception, and to make matters worse, we can't find who are
> > > using
> > > so many memory with "dma_buf_debug_show" since the relevant dma-buf
> > > hasn't exported.
> > >
> > > To make OOM issue easier, maybe need dma-buf framework to dump the
> > > buffer size
> > > under allocating in "dma_buf_debug_show".
> > >
> > > Signed-off-by: Guangming <Guangming.Cao@xxxxxxxxxxxx>
> > > Signed-off-by: jianjiao zeng <jianjiao.zeng@xxxxxxxxxxxx>
> > > ---
> > > v3: 1. update patch, use right shift to replace division.
> > >     2. update patch, add reason in code and commit message.
> > > v2: 1. update size limitation as total_dram page size.
> > >     2. update commit message
> > > ---
> > > drivers/dma-buf/dma-heap.c | 10 ++++++++++
> > > 1 file changed, 10 insertions(+)
> > >
> > > diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
> > > index 56bf5ad01ad5..1fd382712584 100644
> > > --- a/drivers/dma-buf/dma-heap.c
> > > +++ b/drivers/dma-buf/dma-heap.c
> > > @@ -55,6 +55,16 @@ static int dma_heap_buffer_alloc(struct dma_heap
> > > *heap, size_t len,
> > > 	struct dma_buf *dmabuf;
> > > 	int fd;
> > >
> > > +	/*
> > > +	 * Invalid size check. The "len" should be less than totalram.
> > > +	 *
> > > +	 * Without this check, once the invalid size allocation runs on a process
> > > that
> > > +	 * can't be killed by OOM flow(such as "gralloc" on Android devices), it
> > > will
> > > +	 * cause a kernel exception, and to make matters worse, we can't find
> > > who are using
> > > +	 * so many memory with "dma_buf_debug_show" since the relevant
> > > dma-buf hasn't exported.
> > > +	 */
> > > +	if (len >> PAGE_SHIFT > totalram_pages())
> > If your "heap" is from cma, is this still a valid check?
> And thinking a bit further, if I create a heap from something else (say device memory),
> you will need to be able to figure out the maximum allowable check for the specific
> heap.
>
> Maybe the heap needs a callback for max size?

Well we currently maintain a separate allocator and don't use dma-heap, 
but yes we have systems with 16GiB device and only 8GiB system memory so 
that check here is certainly not correct.

In general I would rather let the system run into -ENOMEM or -EINVAL 
from the allocator instead.

Regards,
Christian.

> m
> > M
> >
> > > +		return -EINVAL;
> > > 	/*
> > > 	 * Allocations from all heaps have to begin
> > > 	 * and end on page boundaries.
> > > --
> > > 2.17.1