forked from Minki/linux
fa81511bb0
Checkin:
b3b42ac2cb x86-64, modify_ldt: Ban 16-bit segments on 64-bit kernels
disabled 16-bit segments on 64-bit kernels due to an information
leak. However, it does seem that people are genuinely using Wine to
run old 16-bit Windows programs on Linux.
A proper fix for this ("espfix64") is coming in the upcoming merge
window, but as a temporary fix, create a sysctl to allow the
administrator to re-enable support for 16-bit segments.
It adds a "/proc/sys/abi/ldt16" sysctl that defaults to zero (off). If
you hit this issue and care about your old Windows program more than
you care about a kernel stack address information leak, you can do
echo 1 > /proc/sys/abi/ldt16
as root (add it to your startup scripts), and you should be ok.
The sysctl table is only added if you have COMPAT support enabled on
x86-64, but I assume anybody who runs old windows binaries very much
does that ;)
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/CA%2B55aFw9BPoD10U1LfHbOMpHWZkvJTkMcfCs9s3urPr1YyWBxw@mail.gmail.com
Cc: <stable@vger.kernel.org>
305 lines
6.4 KiB
C
305 lines
6.4 KiB
C
/*
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* (C) Copyright 2002 Linus Torvalds
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* Portions based on the vdso-randomization code from exec-shield:
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* Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
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*
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* This file contains the needed initializations to support sysenter.
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*/
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#include <linux/init.h>
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#include <linux/smp.h>
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#include <linux/thread_info.h>
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#include <linux/sched.h>
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#include <linux/gfp.h>
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#include <linux/string.h>
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#include <linux/elf.h>
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#include <linux/mm.h>
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#include <linux/err.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <asm/cpufeature.h>
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#include <asm/msr.h>
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#include <asm/pgtable.h>
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#include <asm/unistd.h>
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#include <asm/elf.h>
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#include <asm/tlbflush.h>
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#include <asm/vdso.h>
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#include <asm/proto.h>
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#include <asm/fixmap.h>
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#include <asm/hpet.h>
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#include <asm/vvar.h>
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#ifdef CONFIG_COMPAT_VDSO
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#define VDSO_DEFAULT 0
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#else
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#define VDSO_DEFAULT 1
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#endif
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#ifdef CONFIG_X86_64
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#define vdso_enabled sysctl_vsyscall32
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#define arch_setup_additional_pages syscall32_setup_pages
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extern int sysctl_ldt16;
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#endif
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/*
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* Should the kernel map a VDSO page into processes and pass its
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* address down to glibc upon exec()?
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*/
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unsigned int __read_mostly vdso_enabled = VDSO_DEFAULT;
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static int __init vdso_setup(char *s)
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{
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vdso_enabled = simple_strtoul(s, NULL, 0);
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if (vdso_enabled > 1)
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pr_warn("vdso32 values other than 0 and 1 are no longer allowed; vdso disabled\n");
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return 1;
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}
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/*
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* For consistency, the argument vdso32=[012] affects the 32-bit vDSO
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* behavior on both 64-bit and 32-bit kernels.
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* On 32-bit kernels, vdso=[012] means the same thing.
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*/
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__setup("vdso32=", vdso_setup);
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#ifdef CONFIG_X86_32
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__setup_param("vdso=", vdso32_setup, vdso_setup, 0);
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EXPORT_SYMBOL_GPL(vdso_enabled);
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#endif
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static struct page **vdso32_pages;
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static unsigned vdso32_size;
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#ifdef CONFIG_X86_64
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#define vdso32_sysenter() (boot_cpu_has(X86_FEATURE_SYSENTER32))
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#define vdso32_syscall() (boot_cpu_has(X86_FEATURE_SYSCALL32))
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/* May not be __init: called during resume */
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void syscall32_cpu_init(void)
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{
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/* Load these always in case some future AMD CPU supports
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SYSENTER from compat mode too. */
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wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS);
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wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL);
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wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target);
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wrmsrl(MSR_CSTAR, ia32_cstar_target);
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}
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#else /* CONFIG_X86_32 */
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#define vdso32_sysenter() (boot_cpu_has(X86_FEATURE_SEP))
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#define vdso32_syscall() (0)
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void enable_sep_cpu(void)
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{
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int cpu = get_cpu();
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struct tss_struct *tss = &per_cpu(init_tss, cpu);
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if (!boot_cpu_has(X86_FEATURE_SEP)) {
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put_cpu();
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return;
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}
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tss->x86_tss.ss1 = __KERNEL_CS;
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tss->x86_tss.sp1 = sizeof(struct tss_struct) + (unsigned long) tss;
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wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);
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wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0);
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wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0);
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put_cpu();
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}
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#endif /* CONFIG_X86_64 */
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int __init sysenter_setup(void)
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{
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char *vdso32_start, *vdso32_end;
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int npages, i;
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#ifdef CONFIG_COMPAT
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if (vdso32_syscall()) {
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vdso32_start = vdso32_syscall_start;
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vdso32_end = vdso32_syscall_end;
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vdso32_pages = vdso32_syscall_pages;
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} else
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#endif
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if (vdso32_sysenter()) {
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vdso32_start = vdso32_sysenter_start;
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vdso32_end = vdso32_sysenter_end;
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vdso32_pages = vdso32_sysenter_pages;
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} else {
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vdso32_start = vdso32_int80_start;
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vdso32_end = vdso32_int80_end;
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vdso32_pages = vdso32_int80_pages;
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}
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npages = ((vdso32_end - vdso32_start) + PAGE_SIZE - 1) / PAGE_SIZE;
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vdso32_size = npages << PAGE_SHIFT;
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for (i = 0; i < npages; i++)
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vdso32_pages[i] = virt_to_page(vdso32_start + i*PAGE_SIZE);
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patch_vdso32(vdso32_start, vdso32_size);
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return 0;
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}
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/* Setup a VMA at program startup for the vsyscall page */
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int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
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{
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struct mm_struct *mm = current->mm;
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unsigned long addr;
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int ret = 0;
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struct vm_area_struct *vma;
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#ifdef CONFIG_X86_X32_ABI
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if (test_thread_flag(TIF_X32))
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return x32_setup_additional_pages(bprm, uses_interp);
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#endif
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if (vdso_enabled != 1) /* Other values all mean "disabled" */
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return 0;
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down_write(&mm->mmap_sem);
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addr = get_unmapped_area(NULL, 0, vdso32_size + VDSO_OFFSET(VDSO_PREV_PAGES), 0, 0);
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if (IS_ERR_VALUE(addr)) {
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ret = addr;
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goto up_fail;
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}
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addr += VDSO_OFFSET(VDSO_PREV_PAGES);
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current->mm->context.vdso = (void *)addr;
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/*
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* MAYWRITE to allow gdb to COW and set breakpoints
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*/
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ret = install_special_mapping(mm,
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addr,
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vdso32_size,
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VM_READ|VM_EXEC|
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VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
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vdso32_pages);
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if (ret)
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goto up_fail;
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vma = _install_special_mapping(mm,
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addr - VDSO_OFFSET(VDSO_PREV_PAGES),
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VDSO_OFFSET(VDSO_PREV_PAGES),
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VM_READ,
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NULL);
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if (IS_ERR(vma)) {
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ret = PTR_ERR(vma);
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goto up_fail;
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}
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ret = remap_pfn_range(vma,
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addr - VDSO_OFFSET(VDSO_VVAR_PAGE),
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__pa_symbol(&__vvar_page) >> PAGE_SHIFT,
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PAGE_SIZE,
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PAGE_READONLY);
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if (ret)
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goto up_fail;
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#ifdef CONFIG_HPET_TIMER
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if (hpet_address) {
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ret = io_remap_pfn_range(vma,
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addr - VDSO_OFFSET(VDSO_HPET_PAGE),
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hpet_address >> PAGE_SHIFT,
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PAGE_SIZE,
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pgprot_noncached(PAGE_READONLY));
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if (ret)
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goto up_fail;
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}
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#endif
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current_thread_info()->sysenter_return =
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VDSO32_SYMBOL(addr, SYSENTER_RETURN);
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up_fail:
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if (ret)
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current->mm->context.vdso = NULL;
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up_write(&mm->mmap_sem);
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return ret;
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}
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#ifdef CONFIG_X86_64
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subsys_initcall(sysenter_setup);
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#ifdef CONFIG_SYSCTL
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/* Register vsyscall32 into the ABI table */
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#include <linux/sysctl.h>
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static struct ctl_table abi_table2[] = {
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{
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.procname = "vsyscall32",
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.data = &sysctl_vsyscall32,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{
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.procname = "ldt16",
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.data = &sysctl_ldt16,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{}
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};
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static struct ctl_table abi_root_table2[] = {
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{
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.procname = "abi",
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.mode = 0555,
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.child = abi_table2
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},
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{}
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};
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static __init int ia32_binfmt_init(void)
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{
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register_sysctl_table(abi_root_table2);
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return 0;
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}
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__initcall(ia32_binfmt_init);
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#endif
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#else /* CONFIG_X86_32 */
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const char *arch_vma_name(struct vm_area_struct *vma)
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{
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if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso)
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return "[vdso]";
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return NULL;
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}
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struct vm_area_struct *get_gate_vma(struct mm_struct *mm)
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{
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return NULL;
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}
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int in_gate_area(struct mm_struct *mm, unsigned long addr)
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{
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return 0;
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}
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int in_gate_area_no_mm(unsigned long addr)
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{
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return 0;
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}
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#endif /* CONFIG_X86_64 */
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