Messages in this thread | | | From | Geert Uytterhoeven <> | Date | Wed, 6 Jul 2022 23:45:29 +0200 | Subject | Re: [PATCH v2] ARM: Fix MAX_DMA_ADDRESS overflow |
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Hi Florian,
On Wed, Jul 6, 2022 at 10:27 PM Florian Fainelli <f.fainelli@gmail.com> wrote: > On 7/6/22 12:44, Geert Uytterhoeven wrote: > > On Wed, Jul 6, 2022 at 6:46 PM Florian Fainelli <f.fainelli@gmail.com> 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 with the bcm2711 platforms which defines a dma_zone_size > >> of 1GB, and using a PAGE_OFFSET of 0xc000_0000 (CONFIG_VMSPLIT_3G) with > >> CONFIG_DEBUG_VIRTUAL enabled would lead to MAX_DMA_ADDRESS being > >> 0x1_0000_0000 which overflows the unsigned long type used throughout > >> __pa() and __virt_addr_valid(). Because the virtual address passed to > >> __virt_addr_valid() would now be 0, the function would loudly warn, thus > >> making the platform unable to boot properly. > >> > >> Fixes: 26f09e9b3a06 ("mm/memblock: add memblock memory allocation apis") > >> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> > >> --- > >> Changes in v2: > >> > >> - simplify the patch and drop the first patch that attempted to fix an > >> off by one in the calculation. > > > > Thanks for the update! > > > >> --- a/arch/arm/include/asm/dma.h > >> +++ b/arch/arm/include/asm/dma.h > >> @@ -10,7 +10,7 @@ > >> #else > >> #define MAX_DMA_ADDRESS ({ \ > >> extern phys_addr_t arm_dma_zone_size; \ > >> - arm_dma_zone_size && arm_dma_zone_size < (0x10000000 - PAGE_OFFSET) ? \ > > ^^^^^^^^^^ > > 0x10000000ULL, as the constant doesn't fit in 32-bit. > > However, both gcc (9.4.0) and sparse don't seem to complain about > > the missing suffix (anymore?). > > Thanks, I will the ULL suffix in v3.
I just remembered the suffix is not needed (but doesn't hurt), because hexadecimal constants automatically have the right unsigned type.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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