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linux/arch/sparc/kernel/sys_sparc_64.c
Hugh Dickins 1be7107fbe mm: larger stack guard gap, between vmas 
Stack guard page is a useful feature to reduce a risk of stack smashing
into a different mapping. We have been using a single page gap which
is sufficient to prevent having stack adjacent to a different mapping.
But this seems to be insufficient in the light of the stack usage in
userspace. E.g. glibc uses as large as 64kB alloca() in many commonly
used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX]
which is 256kB or stack strings with MAX_ARG_STRLEN.

This will become especially dangerous for suid binaries and the default
no limit for the stack size limit because those applications can be
tricked to consume a large portion of the stack and a single glibc call
could jump over the guard page. These attacks are not theoretical,
unfortunatelly.

Make those attacks less probable by increasing the stack guard gap
to 1MB (on systems with 4k pages; but make it depend on the page size
because systems with larger base pages might cap stack allocations in
the PAGE_SIZE units) which should cover larger alloca() and VLA stack
allocations. It is obviously not a full fix because the problem is
somehow inherent, but it should reduce attack space a lot.

One could argue that the gap size should be configurable from userspace,
but that can be done later when somebody finds that the new 1MB is wrong
for some special case applications.  For now, add a kernel command line
option (stack_guard_gap) to specify the stack gap size (in page units).

Implementation wise, first delete all the old code for stack guard page:
because although we could get away with accounting one extra page in a
stack vma, accounting a larger gap can break userspace - case in point,
a program run with "ulimit -S -v 20000" failed when the 1MB gap was
counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK
and strict non-overcommit mode.

Instead of keeping gap inside the stack vma, maintain the stack guard
gap as a gap between vmas: using vm_start_gap() in place of vm_start
(or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few
places which need to respect the gap - mainly arch_get_unmapped_area(),
and and the vma tree's subtree_gap support for that.

Original-patch-by: Oleg Nesterov <oleg@redhat.com>
Original-patch-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-06-19 21:50:20 +08:00

650 lines
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/* linux/arch/sparc64/kernel/sys_sparc.c
*
* This file contains various random system calls that
* have a non-standard calling sequence on the Linux/sparc
* platform.
*/
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
#include <linux/sched/debug.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/sem.h>
#include <linux/msg.h>
#include <linux/shm.h>
#include <linux/stat.h>
#include <linux/mman.h>
#include <linux/utsname.h>
#include <linux/smp.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/ipc.h>
#include <linux/personality.h>
#include <linux/random.h>
#include <linux/export.h>
#include <linux/context_tracking.h>
#include <linux/uaccess.h>
#include <asm/utrap.h>
#include <asm/unistd.h>
#include "entry.h"
#include "kernel.h"
#include "systbls.h"
/* #define DEBUG_UNIMP_SYSCALL */
asmlinkage unsigned long sys_getpagesize(void)
{
return PAGE_SIZE;
}
/* Does addr --> addr+len fall within 4GB of the VA-space hole or
* overflow past the end of the 64-bit address space?
*/
static inline int invalid_64bit_range(unsigned long addr, unsigned long len)
{
unsigned long va_exclude_start, va_exclude_end;
va_exclude_start = VA_EXCLUDE_START;
va_exclude_end = VA_EXCLUDE_END;
if (unlikely(len >= va_exclude_start))
return 1;
if (unlikely((addr + len) < addr))
return 1;
if (unlikely((addr >= va_exclude_start && addr < va_exclude_end) ||
((addr + len) >= va_exclude_start &&
(addr + len) < va_exclude_end)))
return 1;
return 0;
}
/* These functions differ from the default implementations in
* mm/mmap.c in two ways:
*
* 1) For file backed MAP_SHARED mmap()'s we D-cache color align,
* for fixed such mappings we just validate what the user gave us.
* 2) For 64-bit tasks we avoid mapping anything within 4GB of
* the spitfire/niagara VA-hole.
*/
static inline unsigned long COLOR_ALIGN(unsigned long addr,
unsigned long pgoff)
{
unsigned long base = (addr+SHMLBA-1)&~(SHMLBA-1);
unsigned long off = (pgoff<<PAGE_SHIFT) & (SHMLBA-1);
return base + off;
}
unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct * vma;
unsigned long task_size = TASK_SIZE;
int do_color_align;
struct vm_unmapped_area_info info;
if (flags & MAP_FIXED) {
/* We do not accept a shared mapping if it would violate
* cache aliasing constraints.
*/
if ((flags & MAP_SHARED) &&
((addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1)))
return -EINVAL;
return addr;
}
if (test_thread_flag(TIF_32BIT))
task_size = STACK_TOP32;
if (unlikely(len > task_size || len >= VA_EXCLUDE_START))
return -ENOMEM;
do_color_align = 0;
if (filp || (flags & MAP_SHARED))
do_color_align = 1;
if (addr) {
if (do_color_align)
addr = COLOR_ALIGN(addr, pgoff);
else
addr = PAGE_ALIGN(addr);
vma = find_vma(mm, addr);
if (task_size - len >= addr &&
(!vma || addr + len <= vm_start_gap(vma)))
return addr;
}
info.flags = 0;
info.length = len;
info.low_limit = TASK_UNMAPPED_BASE;
info.high_limit = min(task_size, VA_EXCLUDE_START);
info.align_mask = do_color_align ? (PAGE_MASK & (SHMLBA - 1)) : 0;
info.align_offset = pgoff << PAGE_SHIFT;
addr = vm_unmapped_area(&info);
if ((addr & ~PAGE_MASK) && task_size > VA_EXCLUDE_END) {
VM_BUG_ON(addr != -ENOMEM);
info.low_limit = VA_EXCLUDE_END;
info.high_limit = task_size;
addr = vm_unmapped_area(&info);
}
return addr;
}
unsigned long
arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
const unsigned long len, const unsigned long pgoff,
const unsigned long flags)
{
struct vm_area_struct *vma;
struct mm_struct *mm = current->mm;
unsigned long task_size = STACK_TOP32;
unsigned long addr = addr0;
int do_color_align;
struct vm_unmapped_area_info info;
/* This should only ever run for 32-bit processes. */
BUG_ON(!test_thread_flag(TIF_32BIT));
if (flags & MAP_FIXED) {
/* We do not accept a shared mapping if it would violate
* cache aliasing constraints.
*/
if ((flags & MAP_SHARED) &&
((addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1)))
return -EINVAL;
return addr;
}
if (unlikely(len > task_size))
return -ENOMEM;
do_color_align = 0;
if (filp || (flags & MAP_SHARED))
do_color_align = 1;
/* requesting a specific address */
if (addr) {
if (do_color_align)
addr = COLOR_ALIGN(addr, pgoff);
else
addr = PAGE_ALIGN(addr);
vma = find_vma(mm, addr);
if (task_size - len >= addr &&
(!vma || addr + len <= vm_start_gap(vma)))
return addr;
}
info.flags = VM_UNMAPPED_AREA_TOPDOWN;
info.length = len;
info.low_limit = PAGE_SIZE;
info.high_limit = mm->mmap_base;
info.align_mask = do_color_align ? (PAGE_MASK & (SHMLBA - 1)) : 0;
info.align_offset = pgoff << PAGE_SHIFT;
addr = vm_unmapped_area(&info);
/*
* A failed mmap() very likely causes application failure,
* so fall back to the bottom-up function here. This scenario
* can happen with large stack limits and large mmap()
* allocations.
*/
if (addr & ~PAGE_MASK) {
VM_BUG_ON(addr != -ENOMEM);
info.flags = 0;
info.low_limit = TASK_UNMAPPED_BASE;
info.high_limit = STACK_TOP32;
addr = vm_unmapped_area(&info);
}
return addr;
}
/* Try to align mapping such that we align it as much as possible. */
unsigned long get_fb_unmapped_area(struct file *filp, unsigned long orig_addr, unsigned long len, unsigned long pgoff, unsigned long flags)
{
unsigned long align_goal, addr = -ENOMEM;
unsigned long (*get_area)(struct file *, unsigned long,
unsigned long, unsigned long, unsigned long);
get_area = current->mm->get_unmapped_area;
if (flags & MAP_FIXED) {
/* Ok, don't mess with it. */
return get_area(NULL, orig_addr, len, pgoff, flags);
}
flags &= ~MAP_SHARED;
align_goal = PAGE_SIZE;
if (len >= (4UL * 1024 * 1024))
align_goal = (4UL * 1024 * 1024);
else if (len >= (512UL * 1024))
align_goal = (512UL * 1024);
else if (len >= (64UL * 1024))
align_goal = (64UL * 1024);
do {
addr = get_area(NULL, orig_addr, len + (align_goal - PAGE_SIZE), pgoff, flags);
if (!(addr & ~PAGE_MASK)) {
addr = (addr + (align_goal - 1UL)) & ~(align_goal - 1UL);
break;
}
if (align_goal == (4UL * 1024 * 1024))
align_goal = (512UL * 1024);
else if (align_goal == (512UL * 1024))
align_goal = (64UL * 1024);
else
align_goal = PAGE_SIZE;
} while ((addr & ~PAGE_MASK) && align_goal > PAGE_SIZE);
/* Mapping is smaller than 64K or larger areas could not
* be obtained.
*/
if (addr & ~PAGE_MASK)
addr = get_area(NULL, orig_addr, len, pgoff, flags);
return addr;
}
EXPORT_SYMBOL(get_fb_unmapped_area);
/* Essentially the same as PowerPC. */
static unsigned long mmap_rnd(void)
{
unsigned long rnd = 0UL;
if (current->flags & PF_RANDOMIZE) {
unsigned long val = get_random_long();
if (test_thread_flag(TIF_32BIT))
rnd = (val % (1UL << (23UL-PAGE_SHIFT)));
else
rnd = (val % (1UL << (30UL-PAGE_SHIFT)));
}
return rnd << PAGE_SHIFT;
}
void arch_pick_mmap_layout(struct mm_struct *mm)
{
unsigned long random_factor = mmap_rnd();
unsigned long gap;
/*
* Fall back to the standard layout if the personality
* bit is set, or if the expected stack growth is unlimited:
*/
gap = rlimit(RLIMIT_STACK);
if (!test_thread_flag(TIF_32BIT) ||
(current->personality & ADDR_COMPAT_LAYOUT) ||
gap == RLIM_INFINITY ||
sysctl_legacy_va_layout) {
mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
mm->get_unmapped_area = arch_get_unmapped_area;
} else {
/* We know it's 32-bit */
unsigned long task_size = STACK_TOP32;
if (gap < 128 * 1024 * 1024)
gap = 128 * 1024 * 1024;
if (gap > (task_size / 6 * 5))
gap = (task_size / 6 * 5);
mm->mmap_base = PAGE_ALIGN(task_size - gap - random_factor);
mm->get_unmapped_area = arch_get_unmapped_area_topdown;
}
}
/*
* sys_pipe() is the normal C calling standard for creating
* a pipe. It's not the way unix traditionally does this, though.
*/
SYSCALL_DEFINE1(sparc_pipe_real, struct pt_regs *, regs)
{
int fd[2];
int error;
error = do_pipe_flags(fd, 0);
if (error)
goto out;
regs->u_regs[UREG_I1] = fd[1];
error = fd[0];
out:
return error;
}
/*
* sys_ipc() is the de-multiplexer for the SysV IPC calls..
*
* This is really horribly ugly.
*/
SYSCALL_DEFINE6(sparc_ipc, unsigned int, call, int, first, unsigned long, second,
unsigned long, third, void __user *, ptr, long, fifth)
{
long err;
/* No need for backward compatibility. We can start fresh... */
if (call <= SEMTIMEDOP) {
switch (call) {
case SEMOP:
err = sys_semtimedop(first, ptr,
(unsigned int)second, NULL);
goto out;
case SEMTIMEDOP:
err = sys_semtimedop(first, ptr, (unsigned int)second,
(const struct timespec __user *)
(unsigned long) fifth);
goto out;
case SEMGET:
err = sys_semget(first, (int)second, (int)third);
goto out;
case SEMCTL: {
err = sys_semctl(first, second,
(int)third | IPC_64,
(unsigned long) ptr);
goto out;
}
default:
err = -ENOSYS;
goto out;
}
}
if (call <= MSGCTL) {
switch (call) {
case MSGSND:
err = sys_msgsnd(first, ptr, (size_t)second,
(int)third);
goto out;
case MSGRCV:
err = sys_msgrcv(first, ptr, (size_t)second, fifth,
(int)third);
goto out;
case MSGGET:
err = sys_msgget((key_t)first, (int)second);
goto out;
case MSGCTL:
err = sys_msgctl(first, (int)second | IPC_64, ptr);
goto out;
default:
err = -ENOSYS;
goto out;
}
}
if (call <= SHMCTL) {
switch (call) {
case SHMAT: {
ulong raddr;
err = do_shmat(first, ptr, (int)second, &raddr, SHMLBA);
if (!err) {
if (put_user(raddr,
(ulong __user *) third))
err = -EFAULT;
}
goto out;
}
case SHMDT:
err = sys_shmdt(ptr);
goto out;
case SHMGET:
err = sys_shmget(first, (size_t)second, (int)third);
goto out;
case SHMCTL:
err = sys_shmctl(first, (int)second | IPC_64, ptr);
goto out;
default:
err = -ENOSYS;
goto out;
}
} else {
err = -ENOSYS;
}
out:
return err;
}
SYSCALL_DEFINE1(sparc64_personality, unsigned long, personality)
{
long ret;
if (personality(current->personality) == PER_LINUX32 &&
personality(personality) == PER_LINUX)
personality |= PER_LINUX32;
ret = sys_personality(personality);
if (personality(ret) == PER_LINUX32)
ret &= ~PER_LINUX32;
return ret;
}
int sparc_mmap_check(unsigned long addr, unsigned long len)
{
if (test_thread_flag(TIF_32BIT)) {
if (len >= STACK_TOP32)
return -EINVAL;
if (addr > STACK_TOP32 - len)
return -EINVAL;
} else {
if (len >= VA_EXCLUDE_START)
return -EINVAL;
if (invalid_64bit_range(addr, len))
return -EINVAL;
}
return 0;
}
/* Linux version of mmap */
SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
unsigned long, prot, unsigned long, flags, unsigned long, fd,
unsigned long, off)
{
unsigned long retval = -EINVAL;
if ((off + PAGE_ALIGN(len)) < off)
goto out;
if (off & ~PAGE_MASK)
goto out;
retval = sys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
out:
return retval;
}
SYSCALL_DEFINE2(64_munmap, unsigned long, addr, size_t, len)
{
if (invalid_64bit_range(addr, len))
return -EINVAL;
return vm_munmap(addr, len);
}
SYSCALL_DEFINE5(64_mremap, unsigned long, addr, unsigned long, old_len,
unsigned long, new_len, unsigned long, flags,
unsigned long, new_addr)
{
if (test_thread_flag(TIF_32BIT))
return -EINVAL;
return sys_mremap(addr, old_len, new_len, flags, new_addr);
}
/* we come to here via sys_nis_syscall so it can setup the regs argument */
asmlinkage unsigned long c_sys_nis_syscall(struct pt_regs *regs)
{
static int count;
/* Don't make the system unusable, if someone goes stuck */
if (count++ > 5)
return -ENOSYS;
printk ("Unimplemented SPARC system call %ld\n",regs->u_regs[1]);
#ifdef DEBUG_UNIMP_SYSCALL
show_regs (regs);
#endif
return -ENOSYS;
}
/* #define DEBUG_SPARC_BREAKPOINT */
asmlinkage void sparc_breakpoint(struct pt_regs *regs)
{
enum ctx_state prev_state = exception_enter();
siginfo_t info;
if (test_thread_flag(TIF_32BIT)) {
regs->tpc &= 0xffffffff;
regs->tnpc &= 0xffffffff;
}
#ifdef DEBUG_SPARC_BREAKPOINT
printk ("TRAP: Entering kernel PC=%lx, nPC=%lx\n", regs->tpc, regs->tnpc);
#endif
info.si_signo = SIGTRAP;
info.si_errno = 0;
info.si_code = TRAP_BRKPT;
info.si_addr = (void __user *)regs->tpc;
info.si_trapno = 0;
force_sig_info(SIGTRAP, &info, current);
#ifdef DEBUG_SPARC_BREAKPOINT
printk ("TRAP: Returning to space: PC=%lx nPC=%lx\n", regs->tpc, regs->tnpc);
#endif
exception_exit(prev_state);
}
extern void check_pending(int signum);
SYSCALL_DEFINE2(getdomainname, char __user *, name, int, len)
{
int nlen, err;
if (len < 0)
return -EINVAL;
down_read(&uts_sem);
nlen = strlen(utsname()->domainname) + 1;
err = -EINVAL;
if (nlen > len)
goto out;
err = -EFAULT;
if (!copy_to_user(name, utsname()->domainname, nlen))
err = 0;
out:
up_read(&uts_sem);
return err;
}
SYSCALL_DEFINE5(utrap_install, utrap_entry_t, type,
utrap_handler_t, new_p, utrap_handler_t, new_d,
utrap_handler_t __user *, old_p,
utrap_handler_t __user *, old_d)
{
if (type < UT_INSTRUCTION_EXCEPTION || type > UT_TRAP_INSTRUCTION_31)
return -EINVAL;
if (new_p == (utrap_handler_t)(long)UTH_NOCHANGE) {
if (old_p) {
if (!current_thread_info()->utraps) {
if (put_user(NULL, old_p))
return -EFAULT;
} else {
if (put_user((utrap_handler_t)(current_thread_info()->utraps[type]), old_p))
return -EFAULT;
}
}
if (old_d) {
if (put_user(NULL, old_d))
return -EFAULT;
}
return 0;
}
if (!current_thread_info()->utraps) {
current_thread_info()->utraps =
kzalloc((UT_TRAP_INSTRUCTION_31+1)*sizeof(long), GFP_KERNEL);
if (!current_thread_info()->utraps)
return -ENOMEM;
current_thread_info()->utraps[0] = 1;
} else {
if ((utrap_handler_t)current_thread_info()->utraps[type] != new_p &&
current_thread_info()->utraps[0] > 1) {
unsigned long *p = current_thread_info()->utraps;
current_thread_info()->utraps =
kmalloc((UT_TRAP_INSTRUCTION_31+1)*sizeof(long),
GFP_KERNEL);
if (!current_thread_info()->utraps) {
current_thread_info()->utraps = p;
return -ENOMEM;
}
p[0]--;
current_thread_info()->utraps[0] = 1;
memcpy(current_thread_info()->utraps+1, p+1,
UT_TRAP_INSTRUCTION_31*sizeof(long));
}
}
if (old_p) {
if (put_user((utrap_handler_t)(current_thread_info()->utraps[type]), old_p))
return -EFAULT;
}
if (old_d) {
if (put_user(NULL, old_d))
return -EFAULT;
}
current_thread_info()->utraps[type] = (long)new_p;
return 0;
}
asmlinkage long sparc_memory_ordering(unsigned long model,
struct pt_regs *regs)
{
if (model >= 3)
return -EINVAL;
regs->tstate = (regs->tstate & ~TSTATE_MM) | (model << 14);
return 0;
}
SYSCALL_DEFINE5(rt_sigaction, int, sig, const struct sigaction __user *, act,
struct sigaction __user *, oact, void __user *, restorer,
size_t, sigsetsize)
{
struct k_sigaction new_ka, old_ka;
int ret;
/* XXX: Don't preclude handling different sized sigset_t's. */
if (sigsetsize != sizeof(sigset_t))
return -EINVAL;
if (act) {
new_ka.ka_restorer = restorer;
if (copy_from_user(&new_ka.sa, act, sizeof(*act)))
return -EFAULT;
}
ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
if (!ret && oact) {
if (copy_to_user(oact, &old_ka.sa, sizeof(*oact)))
return -EFAULT;
}
return ret;
}
asmlinkage long sys_kern_features(void)
{
return KERN_FEATURE_MIXED_MODE_STACK;
}
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