mips: use generic mmap top-down layout and brk randomization

mips uses a top-down 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 mips to have elf
randomization and no MMU: without MMU, the security added by randomization
is worth nothing.

Link: http://lkml.kernel.org/r/20190730055113.23635-14-alex@ghiti.fr
Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
Acked-by: Paul Burton <paul.burton@mips.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: James Hogan <jhogan@kernel.org>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index cc8e2b1032a540502ec6d4e937636e41e3c16f6e..a0bd9bdb5f8302ae19e52a0eb7ad1641eca2f5d1 100644 (file)
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -5,7 +5,6 @@ config MIPS
        select ARCH_32BIT_OFF_T if !64BIT
        select ARCH_BINFMT_ELF_STATE if MIPS_FP_SUPPORT
        select ARCH_CLOCKSOURCE_DATA
-       select ARCH_HAS_ELF_RANDOMIZE
        select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
        select ARCH_HAS_UBSAN_SANITIZE_ALL
        select ARCH_SUPPORTS_UPROBES
@@ -13,6 +12,7 @@ config MIPS
        select ARCH_USE_CMPXCHG_LOCKREF if 64BIT
        select ARCH_USE_QUEUED_RWLOCKS
        select ARCH_USE_QUEUED_SPINLOCKS
+       select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
        select ARCH_WANT_IPC_PARSE_VERSION
        select BUILDTIME_EXTABLE_SORT
        select CLONE_BACKWARDS

diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h
index aca909bd784104b9a303f99b2896aec5672e5f19..fba18d4a9190990cedf7ab4bb939a5db92bb5641 100644 (file)
--- a/arch/mips/include/asm/processor.h
+++ b/arch/mips/include/asm/processor.h
@@ -29,11 +29,6 @@
 
 extern unsigned int vced_count, vcei_count;
 
-/*
- * MIPS does have an arch_pick_mmap_layout()
- */
-#define HAVE_ARCH_PICK_MMAP_LAYOUT 1
-
 #ifdef CONFIG_32BIT
 #ifdef CONFIG_KVM_GUEST
 /* User space process size is limited to 1GB in KVM Guest Mode */

diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
index d5106c26ac6a53ec55d3828bd7a4562593ae5e9c..00fe90c6db3e8079323f06d4bf49626fa345014c 100644 (file)
--- a/arch/mips/mm/mmap.c
+++ b/arch/mips/mm/mmap.c
@@ -16,49 +16,10 @@
 #include <linux/random.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/mm.h>
-#include <linux/sizes.h>
-#include <linux/compat.h>
 
 unsigned long shm_align_mask = PAGE_SIZE - 1;  /* Sane caches */
 EXPORT_SYMBOL(shm_align_mask);
 
-/* 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);
-}
-
 #define COLOUR_ALIGN(addr, pgoff)                              \
        ((((addr) + shm_align_mask) & ~shm_align_mask) +        \
         (((pgoff) << PAGE_SHIFT) & shm_align_mask))
@@ -156,63 +117,6 @@ unsigned long arch_get_unmapped_area_topdown(struct file *filp,
                        addr0, len, pgoff, flags, DOWN);
 }
 
-unsigned long arch_mmap_rnd(void)
-{
-       unsigned long rnd;
-
-#ifdef CONFIG_COMPAT
-       if (TASK_IS_32BIT_ADDR)
-               rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
-       else
-#endif /* CONFIG_COMPAT */
-               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;
-       }
-}
-
-static inline unsigned long brk_rnd(void)
-{
-       unsigned long rnd = get_random_long();
-
-       rnd = rnd << PAGE_SHIFT;
-       /* 32MB for 32bit, 1GB for 64bit */
-       if (!IS_ENABLED(CONFIG_64BIT) || is_compat_task())
-               rnd = rnd & (SZ_32M - 1);
-       else
-               rnd = rnd & (SZ_1G - 1);
-
-       return rnd;
-}
-
-unsigned long arch_randomize_brk(struct mm_struct *mm)
-{
-       unsigned long base = mm->brk;
-       unsigned long ret;
-
-       ret = PAGE_ALIGN(base + brk_rnd());
-
-       if (ret < mm->brk)
-               return mm->brk;
-
-       return ret;
-}
-
 bool __virt_addr_valid(const volatile void *kaddr)
 {
        unsigned long vaddr = (unsigned long)kaddr;