Re: [PATCH v3] ARM: Fix MAX_DMA_ADDRESS overflow

From: Florian Fainelli
Date: Wed Jul 13 2022 - 19:28:47 EST

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

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

Fixes: 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis")
Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx>

Shall I send this to RMK's patch system?