On Sun, May 26, 2019 at 09:47:36AM -0400, Alexandre Ghiti wrote: > arm64 handles top-down mmap layout in a way that can be easily reused > by other architectures, so make it available in mm. > It then introduces a new config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > that can be set by other architectures to benefit from those functions. > Note that this new config depends on MMU being enabled, if selected > without MMU support, a warning will be thrown. > > Suggested-by: Christoph Hellwig <[email protected]> > Signed-off-by: Alexandre Ghiti <[email protected]> > Reviewed-by: Christoph Hellwig <[email protected]>
Acked-by: Kees Cook <[email protected]> -Kees > --- > arch/Kconfig | 10 ++++ > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/processor.h | 2 - > arch/arm64/mm/mmap.c | 76 ----------------------------- > kernel/sysctl.c | 6 ++- > mm/util.c | 78 +++++++++++++++++++++++++++++- > 6 files changed, 92 insertions(+), 81 deletions(-) > > diff --git a/arch/Kconfig b/arch/Kconfig > index c47b328eada0..df3ab04270fa 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -701,6 +701,16 @@ config HAVE_ARCH_COMPAT_MMAP_BASES > and vice-versa 32-bit applications to call 64-bit mmap(). > Required for applications doing different bitness syscalls. > > +# This allows to use a set of generic functions to determine mmap base > +# address by giving priority to top-down scheme only if the process > +# is not in legacy mode (compat task, unlimited stack size or > +# sysctl_legacy_va_layout). > +# Architecture that selects this option can provide its own version of: > +# - STACK_RND_MASK > +config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > + bool > + depends on MMU > + > config HAVE_COPY_THREAD_TLS > bool > help > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 4780eb7af842..3d754c19c11e 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -69,6 +69,7 @@ config ARM64 > select ARCH_SUPPORTS_INT128 if GCC_VERSION >= 50000 || CC_IS_CLANG > select ARCH_SUPPORTS_NUMA_BALANCING > select ARCH_WANT_COMPAT_IPC_PARSE_VERSION > + select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > select ARCH_WANT_FRAME_POINTERS > select ARCH_HAS_UBSAN_SANITIZE_ALL > select ARM_AMBA > diff --git a/arch/arm64/include/asm/processor.h > b/arch/arm64/include/asm/processor.h > index fcd0e691b1ea..3bd818edf319 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -282,8 +282,6 @@ static inline void spin_lock_prefetch(const void *ptr) > "nop") : : "p" (ptr)); > } > > -#define HAVE_ARCH_PICK_MMAP_LAYOUT > - > #endif > > extern unsigned long __ro_after_init signal_minsigstksz; /* sigframe size */ > diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c > index ac89686c4af8..c74224421216 100644 > --- a/arch/arm64/mm/mmap.c > +++ b/arch/arm64/mm/mmap.c > @@ -31,82 +31,6 @@ > > #include <asm/cputype.h> > > -/* > - * Leave enough space between the mmap area and the stack to honour ulimit in > - * the face of randomisation. > - */ > -#define MIN_GAP (SZ_128M) > -#define MAX_GAP (STACK_TOP/6*5) > - > -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; > -} > - > -unsigned long arch_mmap_rnd(void) > -{ > - unsigned long rnd; > - > -#ifdef CONFIG_COMPAT > - if (is_compat_task()) > - rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1); > - else > -#endif > - rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1); > - return rnd << PAGE_SHIFT; > -} > - > -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); > -} > - > -/* > - * This function, called very early during the creation of a new process VM > - * image, sets up which VM layout function to use: > - */ > -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(); > - > - /* > - * Fall back to the standard layout if the personality bit is set, or > - * if the expected stack growth is unlimited: > - */ > - 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. > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index 943c89178e3d..aebd03cc4b65 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -271,7 +271,8 @@ extern struct ctl_table epoll_table[]; > extern struct ctl_table firmware_config_table[]; > #endif > > -#ifdef HAVE_ARCH_PICK_MMAP_LAYOUT > +#if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \ > + defined(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT) > int sysctl_legacy_va_layout; > #endif > > @@ -1566,7 +1567,8 @@ static struct ctl_table vm_table[] = { > .proc_handler = proc_dointvec, > .extra1 = &zero, > }, > -#ifdef HAVE_ARCH_PICK_MMAP_LAYOUT > +#if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \ > + defined(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT) > { > .procname = "legacy_va_layout", > .data = &sysctl_legacy_va_layout, > diff --git a/mm/util.c b/mm/util.c > index dab33b896146..717f5d75c16e 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -15,7 +15,12 @@ > #include <linux/vmalloc.h> > #include <linux/userfaultfd_k.h> > #include <linux/elf.h> > +#include <linux/elf-randomize.h> > +#include <linux/personality.h> > #include <linux/random.h> > +#include <linux/processor.h> > +#include <linux/sizes.h> > +#include <linux/compat.h> > > #include <linux/uaccess.h> > > @@ -313,7 +318,78 @@ unsigned long randomize_stack_top(unsigned long > stack_top) > #endif > } > > -#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT) > +#ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > +#ifdef CONFIG_ARCH_HAS_ELF_RANDOMIZE > +unsigned long arch_mmap_rnd(void) > +{ > + unsigned long rnd; > + > +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS > + if (is_compat_task()) > + rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1); > + else > +#endif /* CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS */ > + rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1); > + > + return rnd << PAGE_SHIFT; > +} > +#endif /* CONFIG_ARCH_HAS_ELF_RANDOMIZE */ > + > +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; > +} > + > +/* > + * Leave enough space between the mmap area and the stack to honour ulimit in > + * the face of randomisation. > + */ > +#define MIN_GAP (SZ_128M) > +#define MAX_GAP (STACK_TOP / 6 * 5) > + > +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); > +} > + > +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; > + } > +} > +#elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT) > void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) > { > mm->mmap_base = TASK_UNMAPPED_BASE; > -- > 2.20.1 > -- Kees Cook
