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 Cc: stable@vger.kernel.org Reported-by: Jann Horn jannh@google.com Signed-off-by: Vincenzo Frascino vincenzo.frascino@arm.com --- arch/arm64/include/asm/processor.h | 8 ++++++++ 1 file changed, 8 insertions(+)

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 5d9ce62bdebd..9c831d9d3cd2 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -57,7 +57,15 @@ #define TASK_SIZE_64 (UL(1) << vabits_user)

#ifdef CONFIG_COMPAT +#ifdef CONFIG_ARM64_64K_PAGES +/* + * With CONFIG_ARM64_64K_PAGES enabled, the last page is occupied + * by the compact vectors page. + */ #define TASK_SIZE_32 UL(0x100000000) +#else +#define TASK_SIZE_32 (UL(0x100000000) - PAGE_SIZE) +#endif /* CONFIG_ARM64_64K_PAGES */ #define TASK_SIZE (test_thread_flag(TIF_32BIT) ? \ TASK_SIZE_32 : TASK_SIZE_64) #define TASK_SIZE_OF(tsk) (test_tsk_thread_flag(tsk, TIF_32BIT) ? \