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Commit d2631193 authored by Vincenzo Frascino's avatar Vincenzo Frascino Committed by Will Deacon
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arm64: compat: Reduce address limit 



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: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarVincenzo Frascino <vincenzo.frascino@arm.com>
[will: fixed typo in comment]
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 827a108e

arch/arm64/include/asm/processor.h

+8 −0
Original line number Diff line number Diff line
@@ -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 compat 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) ? \