Messages in this thread Patch in this message | | | Date | Mon, 25 Jan 2021 13:02:04 +0000 | From | Mark Rutland <> | Subject | Re: [PATCH v4 1/3] arm64: Improve kernel address detection of __is_lm_address() |
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Hi Vincenzo,
On Fri, Jan 22, 2021 at 03:56:40PM +0000, Vincenzo Frascino wrote: > Currently, the __is_lm_address() check just masks out the top 12 bits > of the address, but if they are 0, it still yields a true result. > This has as a side effect that virt_addr_valid() returns true even for > invalid virtual addresses (e.g. 0x0). > > Improve the detection checking that it's actually a kernel address > starting at PAGE_OFFSET. > > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > Suggested-by: Catalin Marinas <catalin.marinas@arm.com> > Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Looking around, it seems that there are some existing uses of virt_addr_valid() that expect it to reject addresses outside of the TTBR1 range. For example, check_mem_type() in drivers/tee/optee/call.c.
Given that, I think we need something that's easy to backport to stable.
This patch itself looks fine, but it's not going to backport very far, so I suspect we might need to write a preparatory patch that adds an explicit range check to virt_addr_valid() which can be trivially backported.
For this patch:
Acked-by: Mark Rutland <mark.rutland@arm.com>
Thanks, Mark.
> --- > arch/arm64/include/asm/memory.h | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h > index 18fce223b67b..99d7e1494aaa 100644 > --- a/arch/arm64/include/asm/memory.h > +++ b/arch/arm64/include/asm/memory.h > @@ -247,9 +247,11 @@ static inline const void *__tag_set(const void *addr, u8 tag) > > > /* > - * The linear kernel range starts at the bottom of the virtual address space. > + * Check whether an arbitrary address is within the linear map, which > + * lives in the [PAGE_OFFSET, PAGE_END) interval at the bottom of the > + * kernel's TTBR1 address range. > */ > -#define __is_lm_address(addr) (((u64)(addr) & ~PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET)) > +#define __is_lm_address(addr) (((u64)(addr) ^ PAGE_OFFSET) < (PAGE_END - PAGE_OFFSET)) > > #define __lm_to_phys(addr) (((addr) & ~PAGE_OFFSET) + PHYS_OFFSET) > #define __kimg_to_phys(addr) ((addr) - kimage_voffset) > -- > 2.30.0 >
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