linux/arch/arm64/kernel/vdso.c
Andrei Vagin bcf9964342 arm64/vdso: Restrict splitting VVAR VMA
Forbid splitting VVAR VMA resulting in a stricter ABI and reducing the
amount of corner-cases to consider while working further on VDSO time
namespace support.

As the offset from timens to VVAR page is computed compile-time, the pages
in VVAR should stay together and not being partically mremap()'ed.

Signed-off-by: Andrei Vagin <avagin@gmail.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20200624083321.144975-6-avagin@gmail.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2020-07-24 18:06:52 +01:00

518 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* VDSO implementations.
*
* Copyright (C) 2012 ARM Limited
*
* Author: Will Deacon <will.deacon@arm.com>
*/
#include <linux/cache.h>
#include <linux/clocksource.h>
#include <linux/elf.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/gfp.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/slab.h>
#include <linux/time_namespace.h>
#include <linux/timekeeper_internal.h>
#include <linux/vmalloc.h>
#include <vdso/datapage.h>
#include <vdso/helpers.h>
#include <vdso/vsyscall.h>
#include <asm/cacheflush.h>
#include <asm/signal32.h>
#include <asm/vdso.h>
extern char vdso_start[], vdso_end[];
#ifdef CONFIG_COMPAT_VDSO
extern char vdso32_start[], vdso32_end[];
#endif /* CONFIG_COMPAT_VDSO */
enum vdso_abi {
VDSO_ABI_AA64,
#ifdef CONFIG_COMPAT_VDSO
VDSO_ABI_AA32,
#endif /* CONFIG_COMPAT_VDSO */
};
enum vvar_pages {
VVAR_DATA_PAGE_OFFSET,
VVAR_TIMENS_PAGE_OFFSET,
VVAR_NR_PAGES,
};
struct vdso_abi_info {
const char *name;
const char *vdso_code_start;
const char *vdso_code_end;
unsigned long vdso_pages;
/* Data Mapping */
struct vm_special_mapping *dm;
/* Code Mapping */
struct vm_special_mapping *cm;
};
static struct vdso_abi_info vdso_info[] __ro_after_init = {
[VDSO_ABI_AA64] = {
.name = "vdso",
.vdso_code_start = vdso_start,
.vdso_code_end = vdso_end,
},
#ifdef CONFIG_COMPAT_VDSO
[VDSO_ABI_AA32] = {
.name = "vdso32",
.vdso_code_start = vdso32_start,
.vdso_code_end = vdso32_end,
},
#endif /* CONFIG_COMPAT_VDSO */
};
/*
* The vDSO data page.
*/
static union {
struct vdso_data data[CS_BASES];
u8 page[PAGE_SIZE];
} vdso_data_store __page_aligned_data;
struct vdso_data *vdso_data = vdso_data_store.data;
static int __vdso_remap(enum vdso_abi abi,
const struct vm_special_mapping *sm,
struct vm_area_struct *new_vma)
{
unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
unsigned long vdso_size = vdso_info[abi].vdso_code_end -
vdso_info[abi].vdso_code_start;
if (vdso_size != new_size)
return -EINVAL;
current->mm->context.vdso = (void *)new_vma->vm_start;
return 0;
}
static int __vdso_init(enum vdso_abi abi)
{
int i;
struct page **vdso_pagelist;
unsigned long pfn;
if (memcmp(vdso_info[abi].vdso_code_start, "\177ELF", 4)) {
pr_err("vDSO is not a valid ELF object!\n");
return -EINVAL;
}
vdso_info[abi].vdso_pages = (
vdso_info[abi].vdso_code_end -
vdso_info[abi].vdso_code_start) >>
PAGE_SHIFT;
vdso_pagelist = kcalloc(vdso_info[abi].vdso_pages,
sizeof(struct page *),
GFP_KERNEL);
if (vdso_pagelist == NULL)
return -ENOMEM;
/* Grab the vDSO code pages. */
pfn = sym_to_pfn(vdso_info[abi].vdso_code_start);
for (i = 0; i < vdso_info[abi].vdso_pages; i++)
vdso_pagelist[i] = pfn_to_page(pfn + i);
vdso_info[abi].cm->pages = vdso_pagelist;
return 0;
}
#ifdef CONFIG_TIME_NS
struct vdso_data *arch_get_vdso_data(void *vvar_page)
{
return (struct vdso_data *)(vvar_page);
}
/*
* The vvar mapping contains data for a specific time namespace, so when a task
* changes namespace we must unmap its vvar data for the old namespace.
* Subsequent faults will map in data for the new namespace.
*
* For more details see timens_setup_vdso_data().
*/
int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
{
struct mm_struct *mm = task->mm;
struct vm_area_struct *vma;
mmap_read_lock(mm);
for (vma = mm->mmap; vma; vma = vma->vm_next) {
unsigned long size = vma->vm_end - vma->vm_start;
if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA64].dm))
zap_page_range(vma, vma->vm_start, size);
#ifdef CONFIG_COMPAT_VDSO
if (vma_is_special_mapping(vma, vdso_info[VDSO_ABI_AA32].dm))
zap_page_range(vma, vma->vm_start, size);
#endif
}
mmap_read_unlock(mm);
return 0;
}
static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
{
if (likely(vma->vm_mm == current->mm))
return current->nsproxy->time_ns->vvar_page;
/*
* VM_PFNMAP | VM_IO protect .fault() handler from being called
* through interfaces like /proc/$pid/mem or
* process_vm_{readv,writev}() as long as there's no .access()
* in special_mapping_vmops.
* For more details check_vma_flags() and __access_remote_vm()
*/
WARN(1, "vvar_page accessed remotely");
return NULL;
}
#else
static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
{
return NULL;
}
#endif
static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
struct vm_area_struct *vma, struct vm_fault *vmf)
{
struct page *timens_page = find_timens_vvar_page(vma);
unsigned long pfn;
switch (vmf->pgoff) {
case VVAR_DATA_PAGE_OFFSET:
if (timens_page)
pfn = page_to_pfn(timens_page);
else
pfn = sym_to_pfn(vdso_data);
break;
#ifdef CONFIG_TIME_NS
case VVAR_TIMENS_PAGE_OFFSET:
/*
* If a task belongs to a time namespace then a namespace
* specific VVAR is mapped with the VVAR_DATA_PAGE_OFFSET and
* the real VVAR page is mapped with the VVAR_TIMENS_PAGE_OFFSET
* offset.
* See also the comment near timens_setup_vdso_data().
*/
if (!timens_page)
return VM_FAULT_SIGBUS;
pfn = sym_to_pfn(vdso_data);
break;
#endif /* CONFIG_TIME_NS */
default:
return VM_FAULT_SIGBUS;
}
return vmf_insert_pfn(vma, vmf->address, pfn);
}
static int vvar_mremap(const struct vm_special_mapping *sm,
struct vm_area_struct *new_vma)
{
unsigned long new_size = new_vma->vm_end - new_vma->vm_start;
if (new_size != VVAR_NR_PAGES * PAGE_SIZE)
return -EINVAL;
return 0;
}
static int __setup_additional_pages(enum vdso_abi abi,
struct mm_struct *mm,
struct linux_binprm *bprm,
int uses_interp)
{
unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
unsigned long gp_flags = 0;
void *ret;
BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT;
/* Be sure to map the data page */
vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE;
vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0);
if (IS_ERR_VALUE(vdso_base)) {
ret = ERR_PTR(vdso_base);
goto up_fail;
}
ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE,
VM_READ|VM_MAYREAD|VM_PFNMAP,
vdso_info[abi].dm);
if (IS_ERR(ret))
goto up_fail;
if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
gp_flags = VM_ARM64_BTI;
vdso_base += VVAR_NR_PAGES * PAGE_SIZE;
mm->context.vdso = (void *)vdso_base;
ret = _install_special_mapping(mm, vdso_base, vdso_text_len,
VM_READ|VM_EXEC|gp_flags|
VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
vdso_info[abi].cm);
if (IS_ERR(ret))
goto up_fail;
return 0;
up_fail:
mm->context.vdso = NULL;
return PTR_ERR(ret);
}
#ifdef CONFIG_COMPAT
/*
* Create and map the vectors page for AArch32 tasks.
*/
#ifdef CONFIG_COMPAT_VDSO
static int aarch32_vdso_mremap(const struct vm_special_mapping *sm,
struct vm_area_struct *new_vma)
{
return __vdso_remap(VDSO_ABI_AA32, sm, new_vma);
}
#endif /* CONFIG_COMPAT_VDSO */
enum aarch32_map {
AA32_MAP_VECTORS, /* kuser helpers */
#ifdef CONFIG_COMPAT_VDSO
AA32_MAP_VVAR,
AA32_MAP_VDSO,
#endif
AA32_MAP_SIGPAGE
};
static struct page *aarch32_vectors_page __ro_after_init;
static struct page *aarch32_sig_page __ro_after_init;
static struct vm_special_mapping aarch32_vdso_maps[] = {
[AA32_MAP_VECTORS] = {
.name = "[vectors]", /* ABI */
.pages = &aarch32_vectors_page,
},
#ifdef CONFIG_COMPAT_VDSO
[AA32_MAP_VVAR] = {
.name = "[vvar]",
.fault = vvar_fault,
.mremap = vvar_mremap,
},
[AA32_MAP_VDSO] = {
.name = "[vdso]",
.mremap = aarch32_vdso_mremap,
},
#endif /* CONFIG_COMPAT_VDSO */
[AA32_MAP_SIGPAGE] = {
.name = "[sigpage]", /* ABI */
.pages = &aarch32_sig_page,
},
};
static int aarch32_alloc_kuser_vdso_page(void)
{
extern char __kuser_helper_start[], __kuser_helper_end[];
int kuser_sz = __kuser_helper_end - __kuser_helper_start;
unsigned long vdso_page;
if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
return 0;
vdso_page = get_zeroed_page(GFP_ATOMIC);
if (!vdso_page)
return -ENOMEM;
memcpy((void *)(vdso_page + 0x1000 - kuser_sz), __kuser_helper_start,
kuser_sz);
aarch32_vectors_page = virt_to_page(vdso_page);
flush_dcache_page(aarch32_vectors_page);
return 0;
}
static int aarch32_alloc_sigpage(void)
{
extern char __aarch32_sigret_code_start[], __aarch32_sigret_code_end[];
int sigret_sz = __aarch32_sigret_code_end - __aarch32_sigret_code_start;
unsigned long sigpage;
sigpage = get_zeroed_page(GFP_ATOMIC);
if (!sigpage)
return -ENOMEM;
memcpy((void *)sigpage, __aarch32_sigret_code_start, sigret_sz);
aarch32_sig_page = virt_to_page(sigpage);
flush_dcache_page(aarch32_sig_page);
return 0;
}
#ifdef CONFIG_COMPAT_VDSO
static int __aarch32_alloc_vdso_pages(void)
{
vdso_info[VDSO_ABI_AA32].dm = &aarch32_vdso_maps[AA32_MAP_VVAR];
vdso_info[VDSO_ABI_AA32].cm = &aarch32_vdso_maps[AA32_MAP_VDSO];
return __vdso_init(VDSO_ABI_AA32);
}
#endif /* CONFIG_COMPAT_VDSO */
static int __init aarch32_alloc_vdso_pages(void)
{
int ret;
#ifdef CONFIG_COMPAT_VDSO
ret = __aarch32_alloc_vdso_pages();
if (ret)
return ret;
#endif
ret = aarch32_alloc_sigpage();
if (ret)
return ret;
return aarch32_alloc_kuser_vdso_page();
}
arch_initcall(aarch32_alloc_vdso_pages);
static int aarch32_kuser_helpers_setup(struct mm_struct *mm)
{
void *ret;
if (!IS_ENABLED(CONFIG_KUSER_HELPERS))
return 0;
/*
* Avoid VM_MAYWRITE for compatibility with arch/arm/, where it's
* not safe to CoW the page containing the CPU exception vectors.
*/
ret = _install_special_mapping(mm, AARCH32_VECTORS_BASE, PAGE_SIZE,
VM_READ | VM_EXEC |
VM_MAYREAD | VM_MAYEXEC,
&aarch32_vdso_maps[AA32_MAP_VECTORS]);
return PTR_ERR_OR_ZERO(ret);
}
static int aarch32_sigreturn_setup(struct mm_struct *mm)
{
unsigned long addr;
void *ret;
addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0);
if (IS_ERR_VALUE(addr)) {
ret = ERR_PTR(addr);
goto out;
}
/*
* VM_MAYWRITE is required to allow gdb to Copy-on-Write and
* set breakpoints.
*/
ret = _install_special_mapping(mm, addr, PAGE_SIZE,
VM_READ | VM_EXEC | VM_MAYREAD |
VM_MAYWRITE | VM_MAYEXEC,
&aarch32_vdso_maps[AA32_MAP_SIGPAGE]);
if (IS_ERR(ret))
goto out;
mm->context.sigpage = (void *)addr;
out:
return PTR_ERR_OR_ZERO(ret);
}
int aarch32_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
{
struct mm_struct *mm = current->mm;
int ret;
if (mmap_write_lock_killable(mm))
return -EINTR;
ret = aarch32_kuser_helpers_setup(mm);
if (ret)
goto out;
#ifdef CONFIG_COMPAT_VDSO
ret = __setup_additional_pages(VDSO_ABI_AA32,
mm,
bprm,
uses_interp);
if (ret)
goto out;
#endif /* CONFIG_COMPAT_VDSO */
ret = aarch32_sigreturn_setup(mm);
out:
mmap_write_unlock(mm);
return ret;
}
#endif /* CONFIG_COMPAT */
static int vdso_mremap(const struct vm_special_mapping *sm,
struct vm_area_struct *new_vma)
{
return __vdso_remap(VDSO_ABI_AA64, sm, new_vma);
}
enum aarch64_map {
AA64_MAP_VVAR,
AA64_MAP_VDSO,
};
static struct vm_special_mapping aarch64_vdso_maps[] __ro_after_init = {
[AA64_MAP_VVAR] = {
.name = "[vvar]",
.fault = vvar_fault,
.mremap = vvar_mremap,
},
[AA64_MAP_VDSO] = {
.name = "[vdso]",
.mremap = vdso_mremap,
},
};
static int __init vdso_init(void)
{
vdso_info[VDSO_ABI_AA64].dm = &aarch64_vdso_maps[AA64_MAP_VVAR];
vdso_info[VDSO_ABI_AA64].cm = &aarch64_vdso_maps[AA64_MAP_VDSO];
return __vdso_init(VDSO_ABI_AA64);
}
arch_initcall(vdso_init);
int arch_setup_additional_pages(struct linux_binprm *bprm,
int uses_interp)
{
struct mm_struct *mm = current->mm;
int ret;
if (mmap_write_lock_killable(mm))
return -EINTR;
ret = __setup_additional_pages(VDSO_ABI_AA64,
mm,
bprm,
uses_interp);
mmap_write_unlock(mm);
return ret;
}