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

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Date:   Tue, 28 Mar 2023 11:26:05 -0700
From:   John Stultz <jstultz@...gle.com>
To:     Jaewon Kim <jaewon31.kim@...sung.com>
Cc:     tjmercier@...gle.com, sumit.semwal@...aro.org,
        daniel.vetter@...ll.ch, akpm@...ux-foundation.org,
        hannes@...xchg.org, mhocko@...nel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, jaewon31.kim@...il.com
Subject: Re: [PATCH] dma-buf/heaps: c9e8440eca61 staging: ion: Fix overflow
 and list bugs in system heap:

On Tue, Mar 28, 2023 at 5:58 AM Jaewon Kim <jaewon31.kim@...sung.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@...sung.com>

Hey,
  Thanks so much for sending this out! Looks reasonable to me, the
only issue is the commit subject line could be a bit better.

Maybe instead:
  "dma-buf/heaps: system_heap: Avoid DoS by limiting single
allocations to half of all memory"

Otherwise,
Acked-by: John Stultz <jstultz@...gle.com>

thanks
-john