From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754385AbbL3ENq (ORCPT ); Tue, 29 Dec 2015 23:13:46 -0500 Received: from mail.kernel.org ([198.145.29.136]:56587 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754200AbbL3ENC (ORCPT ); Tue, 29 Dec 2015 23:13:02 -0500 From: Andy Lutomirski To: x86@kernel.org, Borislav Petkov , Kees Cook Cc: linux-kernel@vger.kernel.org, Oleg Nesterov , Andy Lutomirski Subject: [PATCH v3 6/7] x86,vdso: Use .fault instead of remap_pfn_range for the vvar mapping Date: Tue, 29 Dec 2015 20:12:23 -0800 Message-Id: X-Mailer: git-send-email 2.5.0 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is IMO much less ugly, and it also opens the door to disallowing unprivileged userspace HPET access on systems with usable TSCs. Signed-off-by: Andy Lutomirski --- arch/x86/entry/vdso/vma.c | 97 ++++++++++++++++++++++++++++------------------- 1 file changed, 57 insertions(+), 40 deletions(-) diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index eb50d7c1f161..4b5461ba4f6b 100644 --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -102,18 +102,69 @@ static const struct vm_special_mapping text_mapping = { .fault = vdso_fault, }; +static int vvar_fault(const struct vm_special_mapping *sm, + struct vm_area_struct *vma, struct vm_fault *vmf) +{ + const struct vdso_image *image = vma->vm_mm->context.vdso_image; + long sym_offset; + int ret = -EFAULT; + + if (!image) + return VM_FAULT_SIGBUS; + + sym_offset = (long)(vmf->pgoff << PAGE_SHIFT) + + image->sym_vvar_start; + + /* + * Sanity check: a symbol offset of zero means that the page + * does not exist for this vdso image, not that the page is at + * offset zero relative to the text mapping. This should be + * impossible here, because sym_offset should only be zero for + * the page past the end of the vvar mapping. + */ + if (sym_offset == 0) + return VM_FAULT_SIGBUS; + + if (sym_offset == image->sym_vvar_page) { + ret = vm_insert_pfn(vma, (unsigned long)vmf->virtual_address, + __pa_symbol(&__vvar_page) >> PAGE_SHIFT); + } else if (sym_offset == image->sym_hpet_page) { +#ifdef CONFIG_HPET_TIMER + if (hpet_address) { + ret = vm_insert_pfn_prot( + vma, + (unsigned long)vmf->virtual_address, + hpet_address >> PAGE_SHIFT, + pgprot_noncached(PAGE_READONLY)); + } +#endif + } else if (sym_offset == image->sym_pvclock_page) { + struct pvclock_vsyscall_time_info *pvti = + pvclock_pvti_cpu0_va(); + if (pvti) { + ret = vm_insert_pfn( + vma, + (unsigned long)vmf->virtual_address, + __pa(pvti) >> PAGE_SHIFT); + } + } + + if (ret == 0 || ret == -EBUSY) + return VM_FAULT_NOPAGE; + + return VM_FAULT_SIGBUS; +} + static int map_vdso(const struct vdso_image *image, bool calculate_addr) { struct mm_struct *mm = current->mm; struct vm_area_struct *vma; unsigned long addr, text_start; int ret = 0; - static struct page *no_pages[] = {NULL}; - static struct vm_special_mapping vvar_mapping = { + static const struct vm_special_mapping vvar_mapping = { .name = "[vvar]", - .pages = no_pages, + .fault = vvar_fault, }; - struct pvclock_vsyscall_time_info *pvti; if (calculate_addr) { addr = vdso_addr(current->mm->start_stack, @@ -153,7 +204,8 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr) vma = _install_special_mapping(mm, addr, -image->sym_vvar_start, - VM_READ|VM_MAYREAD, + VM_READ|VM_MAYREAD|VM_IO|VM_DONTDUMP| + VM_PFNMAP, &vvar_mapping); if (IS_ERR(vma)) { @@ -161,41 +213,6 @@ static int map_vdso(const struct vdso_image *image, bool calculate_addr) goto up_fail; } - if (image->sym_vvar_page) - ret = remap_pfn_range(vma, - text_start + image->sym_vvar_page, - __pa_symbol(&__vvar_page) >> PAGE_SHIFT, - PAGE_SIZE, - PAGE_READONLY); - - if (ret) - goto up_fail; - -#ifdef CONFIG_HPET_TIMER - if (hpet_address && image->sym_hpet_page) { - ret = io_remap_pfn_range(vma, - text_start + image->sym_hpet_page, - hpet_address >> PAGE_SHIFT, - PAGE_SIZE, - pgprot_noncached(PAGE_READONLY)); - - if (ret) - goto up_fail; - } -#endif - - pvti = pvclock_pvti_cpu0_va(); - if (pvti && image->sym_pvclock_page) { - ret = remap_pfn_range(vma, - text_start + image->sym_pvclock_page, - __pa(pvti) >> PAGE_SHIFT, - PAGE_SIZE, - PAGE_READONLY); - - if (ret) - goto up_fail; - } - up_fail: if (ret) current->mm->context.vdso = NULL; -- 2.5.0