Commit 9035bd29 authored by Alexandre Ghiti's avatar Alexandre Ghiti Committed by Linus Torvalds
Browse files

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: default avatarAlexandre Ghiti <alex@ghiti.fr>
Acked-by: default avatarPaul Burton <paul.burton@mips.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarLuis 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 09036468

arch/mips/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -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

arch/mips/include/asm/processor.h

+0 −5
Original line number Diff line number Diff line
@@ -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 */

arch/mips/mm/mmap.c

+0 −96
Original line number Diff line number Diff line
@@ -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;

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