Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753037AbdL0QtP (ORCPT ); Wed, 27 Dec 2017 11:49:15 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:36286 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753017AbdL0QtK (ORCPT ); Wed, 27 Dec 2017 11:49:10 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andy Lutomirski , Thomas Gleixner , Borislav Petkov , Brian Gerst , Dave Hansen , David Laight , "H. Peter Anvin" , Josh Poimboeuf , Juergen Gross , Kees Cook , Linus Torvalds , Peter Zijlstra , Ingo Molnar Subject: [PATCH 4.14 12/74] x86/vsyscall/64: Explicitly set _PAGE_USER in the pagetable hierarchy Date: Wed, 27 Dec 2017 17:45:45 +0100 Message-Id: <20171227164614.600760541@linuxfoundation.org> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20171227164614.109898944@linuxfoundation.org> References: <20171227164614.109898944@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3249 Lines: 98 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit 49275fef986abfb8b476e4708aaecc07e7d3e087 upstream. The kernel is very erratic as to which pagetables have _PAGE_USER set. The vsyscall page gets lucky: it seems that all of the relevant pagetables are among the apparently arbitrary ones that set _PAGE_USER. Rather than relying on chance, just explicitly set _PAGE_USER. This will let us clean up pagetable setup to stop setting _PAGE_USER. The added code can also be reused by pagetable isolation to manage the _PAGE_USER bit in the usermode tables. [ tglx: Folded paravirt fix from Juergen Gross ] Signed-off-by: Andy Lutomirski Signed-off-by: Thomas Gleixner Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: David Laight Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Kees Cook Cc: Linus Torvalds Cc: Peter Zijlstra Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/entry/vsyscall/vsyscall_64.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) --- a/arch/x86/entry/vsyscall/vsyscall_64.c +++ b/arch/x86/entry/vsyscall/vsyscall_64.c @@ -37,6 +37,7 @@ #include #include #include +#include #define CREATE_TRACE_POINTS #include "vsyscall_trace.h" @@ -329,16 +330,47 @@ int in_gate_area_no_mm(unsigned long add return vsyscall_mode != NONE && (addr & PAGE_MASK) == VSYSCALL_ADDR; } +/* + * The VSYSCALL page is the only user-accessible page in the kernel address + * range. Normally, the kernel page tables can have _PAGE_USER clear, but + * the tables covering VSYSCALL_ADDR need _PAGE_USER set if vsyscalls + * are enabled. + * + * Some day we may create a "minimal" vsyscall mode in which we emulate + * vsyscalls but leave the page not present. If so, we skip calling + * this. + */ +static void __init set_vsyscall_pgtable_user_bits(void) +{ + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd; + + pgd = pgd_offset_k(VSYSCALL_ADDR); + set_pgd(pgd, __pgd(pgd_val(*pgd) | _PAGE_USER)); + p4d = p4d_offset(pgd, VSYSCALL_ADDR); +#if CONFIG_PGTABLE_LEVELS >= 5 + p4d->p4d |= _PAGE_USER; +#endif + pud = pud_offset(p4d, VSYSCALL_ADDR); + set_pud(pud, __pud(pud_val(*pud) | _PAGE_USER)); + pmd = pmd_offset(pud, VSYSCALL_ADDR); + set_pmd(pmd, __pmd(pmd_val(*pmd) | _PAGE_USER)); +} + void __init map_vsyscall(void) { extern char __vsyscall_page; unsigned long physaddr_vsyscall = __pa_symbol(&__vsyscall_page); - if (vsyscall_mode != NONE) + if (vsyscall_mode != NONE) { __set_fixmap(VSYSCALL_PAGE, physaddr_vsyscall, vsyscall_mode == NATIVE ? PAGE_KERNEL_VSYSCALL : PAGE_KERNEL_VVAR); + set_vsyscall_pgtable_user_bits(); + } BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_PAGE) != (unsigned long)VSYSCALL_ADDR);