From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Florian Fainelli <f.fainelli@gmail.com>
Cc: Linux ARM <linux-arm-kernel@lists.infradead.org>,
Russell King <linux@armlinux.org.uk>,
Nicolas Pitre <nico@fluxnic.net>,
Catalin Marinas <catalin.marinas@arm.com>,
open list <linux-kernel@vger.kernel.org>,
Linus Walleij <linus.walleij@linaro.org>,
Rob Herring <robh+dt@kernel.org>,
Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH 2/2] ARM: Clamp MAX_DMA_ADDRESS to 32-bit
Date: Thu, 24 Mar 2022 21:31:56 +0100 [thread overview]
Message-ID: <CAMuHMdWyDLoOit-VYPzLXxLz6W300xpo_wrqj=Pr9sZSwk_OwQ@mail.gmail.com> (raw)
In-Reply-To: <20220324175417.1014562-3-f.fainelli@gmail.com>
Hi Florian,
On Thu, Mar 24, 2022 at 6:54 PM Florian Fainelli <f.fainelli@gmail.com> wrote:
> MAX_DMA_ADDRESS is a virtual address, therefore it needs to fit within a
> 32-bit unsigned quantity. Platforms defining a DMA zone size in
> their machine descriptor can easily overflow this quantity depending on
> the DMA zone size and/or the PAGE_OFFSET setting.
>
> In most cases this is harmless, however in the case of a
> CONFIG_DEBUG_VIRTUAL enabled, __virt_addr_valid() will be unable to
> return that MAX_DMA_ADDRESS is valid because the value passed to that
> function is an unsigned long which has already overflowed.
>
> Fixes: e377cd8221eb ("ARM: 8640/1: Add support for CONFIG_DEBUG_VIRTUAL")
> Fixes: 2fb3ec5c9503 ("ARM: Replace platform definition of ISA_DMA_THRESHOLD/MAX_DMA_ADDRESS")
> Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
> --- a/arch/arm/include/asm/dma.h
> +++ b/arch/arm/include/asm/dma.h
> @@ -8,10 +8,12 @@
> #ifndef CONFIG_ZONE_DMA
> #define MAX_DMA_ADDRESS 0xffffffffUL
> #else
> +#include <linux/minmax.h>
> #define MAX_DMA_ADDRESS ({ \
> extern phys_addr_t arm_dma_zone_size; \
> arm_dma_zone_size && arm_dma_zone_size < (0x10000000 - PAGE_OFFSET) ? \
"arm_dma_zone_size < (0x10000000 - PAGE_OFFSET)" looks
like an overflow-avoiding version of
"PAGE_OFFSET + arm_dma_zone_size < 0x10000000".
However, PAGE_OFFSET is always larger than 0x10000000,
so "0x10000000 - PAGE_OFFSET" is a rather large number?
> - (PAGE_OFFSET + arm_dma_zone_size - 1) : 0xffffffffUL; })
> + min_t(phys_addr_t, (PAGE_OFFSET + arm_dma_zone_size - 1), 0xffffffffUL) : \
> + 0xffffffffUL; })
> #endif
>
> #ifdef CONFIG_ISA_DMA_API
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
next prev parent reply other threads:[~2022-03-24 20:32 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-24 17:54 [PATCH 0/2] ARM: MAX_DMA_ADDRESS fixes Florian Fainelli
2022-03-24 17:54 ` [PATCH 1/2] ARM: Fix off by one in checking DMA zone size Florian Fainelli
2022-03-24 19:02 ` Linus Walleij
2022-04-29 15:15 ` Russell King (Oracle)
2022-04-29 15:45 ` Arnd Bergmann
2022-03-24 17:54 ` [PATCH 2/2] ARM: Clamp MAX_DMA_ADDRESS to 32-bit Florian Fainelli
2022-03-24 19:02 ` Linus Walleij
2022-03-24 20:31 ` Geert Uytterhoeven [this message]
2022-03-24 22:39 ` Florian Fainelli
2022-04-29 15:07 ` Russell King (Oracle)
2022-04-26 16:29 ` [PATCH 0/2] ARM: MAX_DMA_ADDRESS fixes Florian Fainelli
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