linux-kernel - Re: [PATCH v3] ARM: Fix MAX_DMA

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Date:   Tue, 19 Jul 2022 09:34:12 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Russell King <linux@...linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Grygorii Strashko <grygorii.strashko@...com>,
        open list <linux-kernel@...r.kernel.org>, ssantosh@...nel.org,
        ardb@...nel.org, geert+renesas@...der.be
Subject: Re: [PATCH v3] ARM: Fix MAX_DMA_ADDRESS overflow



On 7/18/2022 5:53 AM, Linus Walleij wrote:
> On Thu, Jul 14, 2022 at 1:28 AM Florian Fainelli <f.fainelli@...il.com> wrote:
>> On 7/6/22 13:33, Florian Fainelli wrote:
>>> Commit 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
>>> added a check to determine whether arm_dma_zone_size is exceeding the
>>> amount of kernel virtual address space available between the upper 4GB
>>> virtual address limit and PAGE_OFFSET in order to provide a suitable
>>> definition of MAX_DMA_ADDRESS that should fit within the 32-bit virtual
>>> address space. The quantity used for comparison was off by a missing
>>> trailing 0, leading to MAX_DMA_ADDRESS to be overflowing a 32-bit
>>> quantity.
>>>
>>> This was caught thanks to CONFIG_DEBUG_VIRTUAL on the bcm2711 platform
>>> where we define a dma_zone_size of 1GB and we have a PAGE_OFFSET value
>>> of 0xc000_0000 (CONFIG_VMSPLIT_3G) leading to MAX_DMA_ADDRESS being
>>> 0x1_0000_0000 which overflows the unsigned long type used throughout
>>> __pa() and then __virt_addr_valid(). Because the virtual address passed
>>> to __virt_addr_valid() would now be 0, the function would loudly warn
>>> and flood the kernel log, thus making the platform unable to boot
>>> properly.
>>>
>>> Fixes: 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
>>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>>
>> Shall I send this to RMK's patch system?
> 
> I think so!
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Thanks:

https://www.armlinux.org.uk/developer/patches/viewpatch.php?id=9216/1
-- 
Florian