arm uses a top-down mmap layout by default that exactly fits the generic
functions, so get rid of arch specific code and use the generic version
by selecting ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT.
As ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT selects ARCH_HAS_ELF_RANDOMIZE,
use the generic version of arch_randomize_brk since it also fits.
Note that this commit also removes the possibility for arm to have elf
randomization and no MMU: without MMU, the security added by randomization
is worth nothing.
Note that it is safe to remove STACK_RND_MASK since it matches the default
value.
Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
arch/arm/Kconfig | 2 +-
arch/arm/include/asm/processor.h | 2 --
arch/arm/kernel/process.c | 5 ---
arch/arm/mm/mmap.c | 62 --------------------------------
4 files changed, 1 insertion(+), 70 deletions(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 33b00579beff..81b08b027e4e 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -7,7 +7,6 @@ config ARM
select ARCH_HAS_BINFMT_FLAT
select ARCH_HAS_DEBUG_VIRTUAL if MMU
select ARCH_HAS_DEVMEM_IS_ALLOWED
- select ARCH_HAS_ELF_RANDOMIZE
select ARCH_HAS_FORTIFY_SOURCE
select ARCH_HAS_KEEPINITRD
select ARCH_HAS_KCOV
@@ -30,6 +29,7 @@ config ARM
select ARCH_SUPPORTS_ATOMIC_RMW
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_CMPXCHG_LOCKREF
+ select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
select ARCH_WANT_IPC_PARSE_VERSION
select BINFMT_FLAT_ARGVP_ENVP_ON_STACK
select BUILDTIME_EXTABLE_SORT if MMU
diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index 20c2f42454b8..614bf829e454 100644
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -140,8 +140,6 @@ static inline void prefetchw(const void *ptr)
#endif
#endif
-#define HAVE_ARCH_PICK_MMAP_LAYOUT
-
#endif
#endif /* __ASM_ARM_PROCESSOR_H */
diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index f934a6739fc0..9485acc520a4 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -319,11 +319,6 @@ unsigned long get_wchan(struct task_struct *p)
return 0;
}
-unsigned long arch_randomize_brk(struct mm_struct *mm)
-{
- return randomize_page(mm->brk, 0x02000000);
-}
-
#ifdef CONFIG_MMU
#ifdef CONFIG_KUSER_HELPERS
/*
diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
index 0b94b674aa91..b8d912ac9e61 100644
--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -17,43 +17,6 @@
((((addr)+SHMLBA-1)&~(SHMLBA-1)) + \
(((pgoff)<<PAGE_SHIFT) & (SHMLBA-1)))
-/* gap between mmap and stack */
-#define MIN_GAP (128*1024*1024UL)
-#define MAX_GAP ((STACK_TOP)/6*5)
-#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12))
-
-static int mmap_is_legacy(struct rlimit *rlim_stack)
-{
- if (current->personality & ADDR_COMPAT_LAYOUT)
- return 1;
-
- if (rlim_stack->rlim_cur == RLIM_INFINITY)
- return 1;
-
- return sysctl_legacy_va_layout;
-}
-
-static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
-{
- unsigned long gap = rlim_stack->rlim_cur;
- unsigned long pad = stack_guard_gap;
-
- /* Account for stack randomization if necessary */
- if (current->flags & PF_RANDOMIZE)
- pad += (STACK_RND_MASK << PAGE_SHIFT);
-
- /* Values close to RLIM_INFINITY can overflow. */
- if (gap + pad > gap)
- gap += pad;
-
- if (gap < MIN_GAP)
- gap = MIN_GAP;
- else if (gap > MAX_GAP)
- gap = MAX_GAP;
-
- return PAGE_ALIGN(STACK_TOP - gap - rnd);
-}
-
/*
* We need to ensure that shared mappings are correctly aligned to
* avoid aliasing issues with VIPT caches. We need to ensure that
@@ -181,31 +144,6 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
return addr;
}
-unsigned long arch_mmap_rnd(void)
-{
- unsigned long rnd;
-
- rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
-
- return rnd << PAGE_SHIFT;
-}
-
-void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
-{
- unsigned long random_factor = 0UL;
-
- if (current->flags & PF_RANDOMIZE)
- random_factor = arch_mmap_rnd();
-
- if (mmap_is_legacy(rlim_stack)) {
- mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
- mm->get_unmapped_area = arch_get_unmapped_area;
- } else {
- mm->mmap_base = mmap_base(random_factor, rlim_stack);
- mm->get_unmapped_area = arch_get_unmapped_area_topdown;
- }
-}
-
/*
* You really shouldn't be using read() or write() on /dev/mem. This
* might go away in the future.
--
2.20.1
