Re: [PATCH] dma-buf/heaps: c9e8440eca61 staging: ion: Fix overflow and list bugs in system heap:

["T.J. Mercier" <tjmercier@google.com>]

On Tue, Mar 28, 2023 at 5:58 AM Jaewon Kim <jaewon31.kim@samsung.com> wrote:
>
> Normal free:212600kB min:7664kB low:57100kB high:106536kB
>   reserved_highatomic:4096KB active_anon:276kB inactive_anon:180kB
>   active_file:1200kB inactive_file:0kB unevictable:2932kB
>   writepending:0kB present:4109312kB managed:3689488kB mlocked:2932kB
>   pagetables:13600kB bounce:0kB free_pcp:0kB local_pcp:0kB
>   free_cma:200844kB
> Out of memory and no killable processes...
> Kernel panic - not syncing: System is deadlocked on memory
>
> An OoM panic was reported, there were only native processes which are
> non-killable as OOM_SCORE_ADJ_MIN.
>
> After looking into the dump, I've found the dma-buf system heap was
> trying to allocate a huge size. It seems to be a signed negative value.
>
> dma_heap_ioctl_allocate(inline)
>     |  heap_allocation = 0xFFFFFFC02247BD38 -> (
>     |    len = 0xFFFFFFFFE7225100,
>
> Actually the old ion system heap had policy which does not allow that
> huge size with commit c9e8440eca61 ("staging: ion: Fix overflow and list
> bugs in system heap"). We need this change again. Single allocation
> should not be bigger than half of all memory.
>
> Signed-off-by: Jaewon Kim <jaewon31.kim@samsung.com>
> ---
>  drivers/dma-buf/heaps/system_heap.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
> index e8bd10e60998..4c1ef2ecfb0f 100644
> --- a/drivers/dma-buf/heaps/system_heap.c
> +++ b/drivers/dma-buf/heaps/system_heap.c
> @@ -351,6 +351,9 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap,
>         struct page *page, *tmp_page;
>         int i, ret = -ENOMEM;
>
> +       if (len / PAGE_SIZE > totalram_pages() / 2)
> +               return ERR_PTR(-ENOMEM);
> +

Instead of policy like that, would __GFP_RETRY_MAYFAIL on the system
heap's LOW_ORDER_GFP flags also avoid the panic, and eventually fail
the allocation request?