| Message ID | 20190526134746.9315-9-alex@ghiti.fr (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Provide generic top-down mmap layout functions | expand |
On Sun, May 26, 2019 at 09:47:40AM -0400, Alexandre Ghiti wrote: > 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. > > Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> Acked-by: Kees Cook <keescook@chromium.org> It may be worth noting that STACK_RND_MASK is safe to remove here because it matches the default that now exists in mm/util.c. -Kees > --- > 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 8869742a85df..27687a8c9fb5 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -6,7 +6,6 @@ config ARM > select ARCH_CLOCKSOURCE_DATA > 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 > @@ -29,6 +28,7 @@ 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 BUILDTIME_EXTABLE_SORT if MMU > select CLONE_BACKWARDS > diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h > index 5d06f75ffad4..95b7688341c5 100644 > --- a/arch/arm/include/asm/processor.h > +++ b/arch/arm/include/asm/processor.h > @@ -143,8 +143,6 @@ 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 72cc0862a30e..19a765db5f7f 100644 > --- a/arch/arm/kernel/process.c > +++ b/arch/arm/kernel/process.c > @@ -322,11 +322,6 @@ 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 >
On 5/29/19 3:26 PM, Kees Cook wrote: > On Sun, May 26, 2019 at 09:47:40AM -0400, Alexandre Ghiti wrote: >> 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. >> >> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> > Acked-by: Kees Cook <keescook@chromium.org> > > It may be worth noting that STACK_RND_MASK is safe to remove here > because it matches the default that now exists in mm/util.c. Yes, thanks for pointing that. Thanks, Alex > > -Kees > >> --- >> 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 8869742a85df..27687a8c9fb5 100644 >> --- a/arch/arm/Kconfig >> +++ b/arch/arm/Kconfig >> @@ -6,7 +6,6 @@ config ARM >> select ARCH_CLOCKSOURCE_DATA >> 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 >> @@ -29,6 +28,7 @@ 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 BUILDTIME_EXTABLE_SORT if MMU >> select CLONE_BACKWARDS >> diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h >> index 5d06f75ffad4..95b7688341c5 100644 >> --- a/arch/arm/include/asm/processor.h >> +++ b/arch/arm/include/asm/processor.h >> @@ -143,8 +143,6 @@ 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 72cc0862a30e..19a765db5f7f 100644 >> --- a/arch/arm/kernel/process.c >> +++ b/arch/arm/kernel/process.c >> @@ -322,11 +322,6 @@ 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 >>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 8869742a85df..27687a8c9fb5 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -6,7 +6,6 @@ config ARM select ARCH_CLOCKSOURCE_DATA 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 @@ -29,6 +28,7 @@ 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 BUILDTIME_EXTABLE_SORT if MMU select CLONE_BACKWARDS diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h index 5d06f75ffad4..95b7688341c5 100644 --- a/arch/arm/include/asm/processor.h +++ b/arch/arm/include/asm/processor.h @@ -143,8 +143,6 @@ 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 72cc0862a30e..19a765db5f7f 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -322,11 +322,6 @@ 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.
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. Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> --- 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(-)