On Mon, Apr 01, 2019 at 11:32:01AM +0100, Vincenzo Frascino wrote:
Currently, compat tasks running on arm64 can allocate memory up to TASK_SIZE_32 (UL(0x100000000)).
This means that mmap() allocations, if we treat them as returning an array, are not compliant with the sections 6.5.8 of the C standard (C99) which states that: "If the expression P points to an element of an array object and the expression Q points to the last element of the same array object, the pointer expression Q+1 compares greater than P".
Redefine TASK_SIZE_32 to address the issue.
Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will.deacon@arm.com Cc: Jann Horn jannh@google.com Reported-by: Jann Horn jannh@google.com Signed-off-by: Vincenzo Frascino vincenzo.frascino@arm.com
arch/arm64/include/asm/processor.h | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 5d9ce62bdebd..f8235f7df29b 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -57,7 +57,11 @@ #define TASK_SIZE_64 (UL(1) << vabits_user) #ifdef CONFIG_COMPAT +#ifdef CONFIG_ARM64_64K_PAGES #define TASK_SIZE_32 UL(0x100000000) +#else +#define TASK_SIZE_32 (UL(0x100000000) - PAGE_SIZE) +#endif /* CONFIG_ARM64_64K_PAGES */
I'd add a comment above stating that with the 64K page configuration, the last page is occupied by the compat vectors page.