Am 13.01.22 um 14:00 schrieb Ruhl, Michael J:
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Ruhl, Michael J
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Subject: RE: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation
-----Original Message-----
From: dri-devel <dri-devel-boun...@lists.freedesktop.org> On Behalf Of
guangming....@mediatek.com
Sent: Thursday, January 13, 2022 7:34 AM
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Subject: [PATCH v3] dma-buf: dma-heap: Add a size check for allocation
From: Guangming <guangming....@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....@mediatek.com>
Signed-off-by: jianjiao zeng <jianjiao.z...@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
