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@xxxxxxx> > Cc: Will Deacon <will.deacon@xxxxxxx> > Cc: Jann Horn <jannh@xxxxxxxxxx> > Reported-by: Jann Horn <jannh@xxxxxxxxxx> > Signed-off-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> > --- > 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. -- Catalin
