From: Guangming <Guangming.Cao@mediatek.com>

Currently, there is no size check for allocation.

If the alloc size is larger than DRAM, it will cause OOM issue.
Besides, if it runs on a process that won't be killed by OOM flow, it will
cause a kernel exception finally,  and we couldn't find the correct
memory usage by dma-buf dump api such as "dma_buf_debug_show" since the
allocation is still on going and the corresponding dmabuf is not exported.

However, it sounds not simple enough to adding a count to count how many
pages has been allocated before allocating done.
So adding a size limitation here to prevent this case.

Signed-off-by: Guangming <Guangming.Cao@mediatek.com>
Signed-off-by: jianjiao zeng <jianjiao.zeng@mediatek.com>
---
 drivers/dma-buf/dma-heap.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
index 56bf5ad01ad5..8b75998a106c 100644
--- a/drivers/dma-buf/dma-heap.c
+++ b/drivers/dma-buf/dma-heap.c
@@ -107,6 +107,9 @@ static long dma_heap_ioctl_allocate(struct file *file, void *data)
 	if (heap_allocation->heap_flags & ~DMA_HEAP_VALID_HEAP_FLAGS)
 		return -EINVAL;
 
+	if (heap_allocation->len / PAGE_SIZE > totalram_pages() / 2)
+		return -EINVAL;
+
 	fd = dma_heap_buffer_alloc(heap, heap_allocation->len,
 				   heap_allocation->fd_flags,
 				   heap_allocation->heap_flags);
-- 
2.17.1

From: Guangming <Guangming.Cao@mediatek.com>

Add a size check for allcation since the allocation size is
always less than the total DRAM size.

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;
 	/*
 	 * Allocations from all heaps have to begin
 	 * and end on page boundaries.
-- 
2.17.1

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?


> 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

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.

>
>
>> 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

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.
Thanks :)
Guangming

> > 
> > 
> > > 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
> 
> 

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

From: Guangming <Guangming.Cao@mediatek.com>

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@mediatek.com>
Signed-off-by: jianjiao zeng <jianjiao.zeng@mediatek.com>
---
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())
+		return -EINVAL;
 	/*
 	 * Allocations from all heaps have to begin
 	 * and end on page boundaries.
-- 
2.17.1

>-----Original Message-----
>From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
>guangming.cao@mediatek.com
>Sent: Thursday, January 13, 2022 7:34 AM
>To: sumit.semwal@linaro.org
>Cc: linux-arm-kernel@lists.infradead.org; mingyuan.ma@mediatek.com;
>Guangming <Guangming.Cao@mediatek.com>;
>wsd_upstream@mediatek.com; linux-kernel@vger.kernel.org; dri-
>devel@lists.freedesktop.org; linaro-mm-sig@lists.linaro.org;
>yf.wang@mediatek.com; libo.kang@mediatek.com;
>benjamin.gaignard@linaro.org; bo.song@mediatek.com;
>matthias.bgg@gmail.com; linux-mediatek@lists.infradead.org;
>lmark@codeaurora.org; labbott@redhat.com; christian.koenig@amd.com;
>jianjiao.zeng@mediatek.com; linux-media@vger.kernel.org
>Subject: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation
>
>From: Guangming <Guangming.Cao@mediatek.com>
>
>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@mediatek.com>
>Signed-off-by: jianjiao zeng <jianjiao.zeng@mediatek.com>
>---
>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?

M

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

>-----Original Message-----
>From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
>Ruhl, Michael J
>Sent: Thursday, January 13, 2022 7:58 AM
>To: guangming.cao@mediatek.com; sumit.semwal@linaro.org
>Cc: jianjiao.zeng@mediatek.com; lmark@codeaurora.org;
>wsd_upstream@mediatek.com; christian.koenig@amd.com; linux-
>kernel@vger.kernel.org; dri-devel@lists.freedesktop.org;
>yf.wang@mediatek.com; linaro-mm-sig@lists.linaro.org; linux-
>mediatek@lists.infradead.org; libo.kang@mediatek.com;
>benjamin.gaignard@linaro.org; bo.song@mediatek.com;
>matthias.bgg@gmail.com; labbott@redhat.com;
>mingyuan.ma@mediatek.com; linux-arm-kernel@lists.infradead.org; linux-
>media@vger.kernel.org
>Subject: RE: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation
>
>
>>-----Original Message-----
>>From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
>>guangming.cao@mediatek.com
>>Sent: Thursday, January 13, 2022 7:34 AM
>>To: sumit.semwal@linaro.org
>>Cc: linux-arm-kernel@lists.infradead.org; mingyuan.ma@mediatek.com;
>>Guangming <Guangming.Cao@mediatek.com>;
>>wsd_upstream@mediatek.com; linux-kernel@vger.kernel.org; dri-
>>devel@lists.freedesktop.org; linaro-mm-sig@lists.linaro.org;
>>yf.wang@mediatek.com; libo.kang@mediatek.com;
>>benjamin.gaignard@linaro.org; bo.song@mediatek.com;
>>matthias.bgg@gmail.com; linux-mediatek@lists.infradead.org;
>>lmark@codeaurora.org; labbott@redhat.com; christian.koenig@amd.com;
>>jianjiao.zeng@mediatek.com; linux-media@vger.kernel.org
>>Subject: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation
>>
>>From: Guangming <Guangming.Cao@mediatek.com>
>>
>>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@mediatek.com>
>>Signed-off-by: jianjiao zeng <jianjiao.zeng@mediatek.com>
>>---
>>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?

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

Am 13.01.22 um 14:00 schrieb Ruhl, Michael J:
>> -----Original Message-----
>> From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
>> Ruhl, Michael J
>> Sent: Thursday, January 13, 2022 7:58 AM
>> To: guangming.cao@mediatek.com; sumit.semwal@linaro.org
>> Cc: jianjiao.zeng@mediatek.com; lmark@codeaurora.org;
>> wsd_upstream@mediatek.com; christian.koenig@amd.com; linux-
>> kernel@vger.kernel.org; dri-devel@lists.freedesktop.org;
>> yf.wang@mediatek.com; linaro-mm-sig@lists.linaro.org; linux-
>> mediatek@lists.infradead.org; libo.kang@mediatek.com;
>> benjamin.gaignard@linaro.org; bo.song@mediatek.com;
>> matthias.bgg@gmail.com; labbott@redhat.com;
>> mingyuan.ma@mediatek.com; linux-arm-kernel@lists.infradead.org; linux-
>> media@vger.kernel.org
>> Subject: RE: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation
>>
>>
>>> -----Original Message-----
>>> From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
>>> guangming.cao@mediatek.com
>>> Sent: Thursday, January 13, 2022 7:34 AM
>>> To: sumit.semwal@linaro.org
>>> Cc: linux-arm-kernel@lists.infradead.org; mingyuan.ma@mediatek.com;
>>> Guangming <Guangming.Cao@mediatek.com>;
>>> wsd_upstream@mediatek.com; linux-kernel@vger.kernel.org; dri-
>>> devel@lists.freedesktop.org; linaro-mm-sig@lists.linaro.org;
>>> yf.wang@mediatek.com; libo.kang@mediatek.com;
>>> benjamin.gaignard@linaro.org; bo.song@mediatek.com;
>>> matthias.bgg@gmail.com; linux-mediatek@lists.infradead.org;
>>> lmark@codeaurora.org; labbott@redhat.com; christian.koenig@amd.com;
>>> jianjiao.zeng@mediatek.com; linux-media@vger.kernel.org
>>> Subject: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation
>>>
>>> From: Guangming <Guangming.Cao@mediatek.com>
>>>
>>> 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@mediatek.com>
>>> Signed-off-by: jianjiao zeng <jianjiao.zeng@mediatek.com>
>>> ---
>>> 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

On Thu, Jan 13, 2022 at 5:05 AM Christian König
<christian.koenig@amd.com> wrote:
> Am 13.01.22 um 14:00 schrieb Ruhl, Michael J:
> >> -----Original Message-----
> >> From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
> >> Ruhl, Michael J
> >>> -----Original Message-----
> >>> From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
> >>> guangming.cao@mediatek.com
> >>> +   /*
> >>> +    * 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.

Good point.

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

Probably the simpler solution is to push the allocation check to the
heap driver, rather than doing it at the top level here.

For CMA or other contiguous heaps, letting the allocator fail is fast
enough. For noncontiguous buffers, like the system heap, the
allocation can burn a lot of time and consume a lot of memory (causing
other trouble) before a large allocation might naturally fail.

thanks
-john

Am 14.01.22 um 00:26 schrieb John Stultz:
> On Thu, Jan 13, 2022 at 5:05 AM Christian König
> <christian.koenig@amd.com> wrote:
>> Am 13.01.22 um 14:00 schrieb Ruhl, Michael J:
>>>> -----Original Message-----
>>>> From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
>>>> Ruhl, Michael J
>>>>> -----Original Message-----
>>>>> From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of
>>>>> guangming.cao@mediatek.com
>>>>> +   /*
>>>>> +    * 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.
> Good point.
>
>> In general I would rather let the system run into -ENOMEM or -EINVAL
>> from the allocator instead.
> Probably the simpler solution is to push the allocation check to the
> heap driver, rather than doing it at the top level here.
>
> For CMA or other contiguous heaps, letting the allocator fail is fast
> enough. For noncontiguous buffers, like the system heap, the
> allocation can burn a lot of time and consume a lot of memory (causing
> other trouble) before a large allocation might naturally fail.

Yeah, letting a alloc_page() loop run for a while is usually not nice at 
all :)

You can still do a sanity check here, e.g. the size should never have 
the most significant bit set for example.

Regards,
Christian.

>
> thanks
> -john