forked from Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
250 lines
7.0 KiB
250 lines
7.0 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
|
/* |
|
* Flexible mmap layout support |
|
* |
|
* Based on code by Ingo Molnar and Andi Kleen, copyrighted |
|
* as follows: |
|
* |
|
* Copyright 2003-2009 Red Hat Inc. |
|
* All Rights Reserved. |
|
* Copyright 2005 Andi Kleen, SUSE Labs. |
|
* Copyright 2007 Jiri Kosina, SUSE Labs. |
|
*/ |
|
|
|
#include <linux/personality.h> |
|
#include <linux/mm.h> |
|
#include <linux/random.h> |
|
#include <linux/limits.h> |
|
#include <linux/sched/signal.h> |
|
#include <linux/sched/mm.h> |
|
#include <linux/compat.h> |
|
#include <linux/elf-randomize.h> |
|
#include <asm/elf.h> |
|
#include <asm/io.h> |
|
|
|
#include "physaddr.h" |
|
|
|
struct va_alignment __read_mostly va_align = { |
|
.flags = -1, |
|
}; |
|
|
|
unsigned long task_size_32bit(void) |
|
{ |
|
return IA32_PAGE_OFFSET; |
|
} |
|
|
|
unsigned long task_size_64bit(int full_addr_space) |
|
{ |
|
return full_addr_space ? TASK_SIZE_MAX : DEFAULT_MAP_WINDOW; |
|
} |
|
|
|
static unsigned long stack_maxrandom_size(unsigned long task_size) |
|
{ |
|
unsigned long max = 0; |
|
if (current->flags & PF_RANDOMIZE) { |
|
max = (-1UL) & __STACK_RND_MASK(task_size == task_size_32bit()); |
|
max <<= PAGE_SHIFT; |
|
} |
|
|
|
return max; |
|
} |
|
|
|
#ifdef CONFIG_COMPAT |
|
# define mmap32_rnd_bits mmap_rnd_compat_bits |
|
# define mmap64_rnd_bits mmap_rnd_bits |
|
#else |
|
# define mmap32_rnd_bits mmap_rnd_bits |
|
# define mmap64_rnd_bits mmap_rnd_bits |
|
#endif |
|
|
|
#define SIZE_128M (128 * 1024 * 1024UL) |
|
|
|
static int mmap_is_legacy(void) |
|
{ |
|
if (current->personality & ADDR_COMPAT_LAYOUT) |
|
return 1; |
|
|
|
return sysctl_legacy_va_layout; |
|
} |
|
|
|
static unsigned long arch_rnd(unsigned int rndbits) |
|
{ |
|
if (!(current->flags & PF_RANDOMIZE)) |
|
return 0; |
|
return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT; |
|
} |
|
|
|
unsigned long arch_mmap_rnd(void) |
|
{ |
|
return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits); |
|
} |
|
|
|
static unsigned long mmap_base(unsigned long rnd, unsigned long task_size, |
|
struct rlimit *rlim_stack) |
|
{ |
|
unsigned long gap = rlim_stack->rlim_cur; |
|
unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap; |
|
unsigned long gap_min, gap_max; |
|
|
|
/* Values close to RLIM_INFINITY can overflow. */ |
|
if (gap + pad > gap) |
|
gap += pad; |
|
|
|
/* |
|
* Top of mmap area (just below the process stack). |
|
* Leave an at least ~128 MB hole with possible stack randomization. |
|
*/ |
|
gap_min = SIZE_128M; |
|
gap_max = (task_size / 6) * 5; |
|
|
|
if (gap < gap_min) |
|
gap = gap_min; |
|
else if (gap > gap_max) |
|
gap = gap_max; |
|
|
|
return PAGE_ALIGN(task_size - gap - rnd); |
|
} |
|
|
|
static unsigned long mmap_legacy_base(unsigned long rnd, |
|
unsigned long task_size) |
|
{ |
|
return __TASK_UNMAPPED_BASE(task_size) + rnd; |
|
} |
|
|
|
/* |
|
* This function, called very early during the creation of a new |
|
* process VM image, sets up which VM layout function to use: |
|
*/ |
|
static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base, |
|
unsigned long random_factor, unsigned long task_size, |
|
struct rlimit *rlim_stack) |
|
{ |
|
*legacy_base = mmap_legacy_base(random_factor, task_size); |
|
if (mmap_is_legacy()) |
|
*base = *legacy_base; |
|
else |
|
*base = mmap_base(random_factor, task_size, rlim_stack); |
|
} |
|
|
|
void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) |
|
{ |
|
if (mmap_is_legacy()) |
|
mm->get_unmapped_area = arch_get_unmapped_area; |
|
else |
|
mm->get_unmapped_area = arch_get_unmapped_area_topdown; |
|
|
|
arch_pick_mmap_base(&mm->mmap_base, &mm->mmap_legacy_base, |
|
arch_rnd(mmap64_rnd_bits), task_size_64bit(0), |
|
rlim_stack); |
|
|
|
#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES |
|
/* |
|
* The mmap syscall mapping base decision depends solely on the |
|
* syscall type (64-bit or compat). This applies for 64bit |
|
* applications and 32bit applications. The 64bit syscall uses |
|
* mmap_base, the compat syscall uses mmap_compat_base. |
|
*/ |
|
arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base, |
|
arch_rnd(mmap32_rnd_bits), task_size_32bit(), |
|
rlim_stack); |
|
#endif |
|
} |
|
|
|
unsigned long get_mmap_base(int is_legacy) |
|
{ |
|
struct mm_struct *mm = current->mm; |
|
|
|
#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES |
|
if (in_32bit_syscall()) { |
|
return is_legacy ? mm->mmap_compat_legacy_base |
|
: mm->mmap_compat_base; |
|
} |
|
#endif |
|
return is_legacy ? mm->mmap_legacy_base : mm->mmap_base; |
|
} |
|
|
|
const char *arch_vma_name(struct vm_area_struct *vma) |
|
{ |
|
return NULL; |
|
} |
|
|
|
/** |
|
* mmap_address_hint_valid - Validate the address hint of mmap |
|
* @addr: Address hint |
|
* @len: Mapping length |
|
* |
|
* Check whether @addr and @addr + @len result in a valid mapping. |
|
* |
|
* On 32bit this only checks whether @addr + @len is <= TASK_SIZE. |
|
* |
|
* On 64bit with 5-level page tables another sanity check is required |
|
* because mappings requested by mmap(@addr, 0) which cross the 47-bit |
|
* virtual address boundary can cause the following theoretical issue: |
|
* |
|
* An application calls mmap(addr, 0), i.e. without MAP_FIXED, where @addr |
|
* is below the border of the 47-bit address space and @addr + @len is |
|
* above the border. |
|
* |
|
* With 4-level paging this request succeeds, but the resulting mapping |
|
* address will always be within the 47-bit virtual address space, because |
|
* the hint address does not result in a valid mapping and is |
|
* ignored. Hence applications which are not prepared to handle virtual |
|
* addresses above 47-bit work correctly. |
|
* |
|
* With 5-level paging this request would be granted and result in a |
|
* mapping which crosses the border of the 47-bit virtual address |
|
* space. If the application cannot handle addresses above 47-bit this |
|
* will lead to misbehaviour and hard to diagnose failures. |
|
* |
|
* Therefore ignore address hints which would result in a mapping crossing |
|
* the 47-bit virtual address boundary. |
|
* |
|
* Note, that in the same scenario with MAP_FIXED the behaviour is |
|
* different. The request with @addr < 47-bit and @addr + @len > 47-bit |
|
* fails on a 4-level paging machine but succeeds on a 5-level paging |
|
* machine. It is reasonable to expect that an application does not rely on |
|
* the failure of such a fixed mapping request, so the restriction is not |
|
* applied. |
|
*/ |
|
bool mmap_address_hint_valid(unsigned long addr, unsigned long len) |
|
{ |
|
if (TASK_SIZE - len < addr) |
|
return false; |
|
|
|
return (addr > DEFAULT_MAP_WINDOW) == (addr + len > DEFAULT_MAP_WINDOW); |
|
} |
|
|
|
/* Can we access it for direct reading/writing? Must be RAM: */ |
|
int valid_phys_addr_range(phys_addr_t addr, size_t count) |
|
{ |
|
return addr + count - 1 <= __pa(high_memory - 1); |
|
} |
|
|
|
/* Can we access it through mmap? Must be a valid physical address: */ |
|
int valid_mmap_phys_addr_range(unsigned long pfn, size_t count) |
|
{ |
|
phys_addr_t addr = (phys_addr_t)pfn << PAGE_SHIFT; |
|
|
|
return phys_addr_valid(addr + count - 1); |
|
} |
|
|
|
/* |
|
* Only allow root to set high MMIO mappings to PROT_NONE. |
|
* This prevents an unpriv. user to set them to PROT_NONE and invert |
|
* them, then pointing to valid memory for L1TF speculation. |
|
* |
|
* Note: for locked down kernels may want to disable the root override. |
|
*/ |
|
bool pfn_modify_allowed(unsigned long pfn, pgprot_t prot) |
|
{ |
|
if (!boot_cpu_has_bug(X86_BUG_L1TF)) |
|
return true; |
|
if (!__pte_needs_invert(pgprot_val(prot))) |
|
return true; |
|
/* If it's real memory always allow */ |
|
if (pfn_valid(pfn)) |
|
return true; |
|
if (pfn >= l1tf_pfn_limit() && !capable(CAP_SYS_ADMIN)) |
|
return false; |
|
return true; |
|
}
|
|
|