Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933218AbeAHNDU (ORCPT + 1 other); Mon, 8 Jan 2018 08:03:20 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:45090 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933203AbeAHNDR (ORCPT ); Mon, 8 Jan 2018 08:03:17 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Borislav Petkov , Hugh Dickins Subject: [PATCH 4.4 22/22] Map the vsyscall page with _PAGE_USER Date: Mon, 8 Jan 2018 13:59:49 +0100 Message-Id: <20180108125926.547543023@linuxfoundation.org> X-Mailer: git-send-email 2.15.1 In-Reply-To: <20180108125925.601688333@linuxfoundation.org> References: <20180108125925.601688333@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 Return-Path: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Borislav Petkov This needs to happen early in kaiser_pagetable_walk(), before the hierarchy is established so that _PAGE_USER permission can be really set. A proper fix would be to teach kaiser_pagetable_walk() to update those permissions but the vsyscall page is the only exception here so ... Signed-off-by: Borislav Petkov Acked-by: Hugh Dickins Signed-off-by: Greg Kroah-Hartman --- arch/x86/entry/vsyscall/vsyscall_64.c | 5 +++++ arch/x86/include/asm/vsyscall.h | 2 ++ arch/x86/mm/kaiser.c | 34 ++++++++++++++++++++++++++++++---- 3 files changed, 37 insertions(+), 4 deletions(-) --- a/arch/x86/entry/vsyscall/vsyscall_64.c +++ b/arch/x86/entry/vsyscall/vsyscall_64.c @@ -66,6 +66,11 @@ static int __init vsyscall_setup(char *s } early_param("vsyscall", vsyscall_setup); +bool vsyscall_enabled(void) +{ + return vsyscall_mode != NONE; +} + static void warn_bad_vsyscall(const char *level, struct pt_regs *regs, const char *message) { --- a/arch/x86/include/asm/vsyscall.h +++ b/arch/x86/include/asm/vsyscall.h @@ -12,12 +12,14 @@ extern void map_vsyscall(void); * Returns true if handled. */ extern bool emulate_vsyscall(struct pt_regs *regs, unsigned long address); +extern bool vsyscall_enabled(void); #else static inline void map_vsyscall(void) {} static inline bool emulate_vsyscall(struct pt_regs *regs, unsigned long address) { return false; } +bool vsyscall_enabled(void) { return false; } #endif #endif /* _ASM_X86_VSYSCALL_H */ --- a/arch/x86/mm/kaiser.c +++ b/arch/x86/mm/kaiser.c @@ -20,6 +20,7 @@ #include #include #include +#include int kaiser_enabled __read_mostly = 1; EXPORT_SYMBOL(kaiser_enabled); /* for inlined TLB flush functions */ @@ -111,12 +112,13 @@ static inline unsigned long get_pa_from_ * * Returns a pointer to a PTE on success, or NULL on failure. */ -static pte_t *kaiser_pagetable_walk(unsigned long address) +static pte_t *kaiser_pagetable_walk(unsigned long address, bool user) { pmd_t *pmd; pud_t *pud; pgd_t *pgd = native_get_shadow_pgd(pgd_offset_k(address)); gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO); + unsigned long prot = _KERNPG_TABLE; if (pgd_none(*pgd)) { WARN_ONCE(1, "All shadow pgds should have been populated"); @@ -124,6 +126,17 @@ static pte_t *kaiser_pagetable_walk(unsi } BUILD_BUG_ON(pgd_large(*pgd) != 0); + if (user) { + /* + * The vsyscall page is the only page that will have + * _PAGE_USER set. Catch everything else. + */ + BUG_ON(address != VSYSCALL_ADDR); + + set_pgd(pgd, __pgd(pgd_val(*pgd) | _PAGE_USER)); + prot = _PAGE_TABLE; + } + pud = pud_offset(pgd, address); /* The shadow page tables do not use large mappings: */ if (pud_large(*pud)) { @@ -136,7 +149,7 @@ static pte_t *kaiser_pagetable_walk(unsi return NULL; spin_lock(&shadow_table_allocation_lock); if (pud_none(*pud)) { - set_pud(pud, __pud(_KERNPG_TABLE | __pa(new_pmd_page))); + set_pud(pud, __pud(prot | __pa(new_pmd_page))); __inc_zone_page_state(virt_to_page((void *) new_pmd_page), NR_KAISERTABLE); } else @@ -156,7 +169,7 @@ static pte_t *kaiser_pagetable_walk(unsi return NULL; spin_lock(&shadow_table_allocation_lock); if (pmd_none(*pmd)) { - set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page))); + set_pmd(pmd, __pmd(prot | __pa(new_pte_page))); __inc_zone_page_state(virt_to_page((void *) new_pte_page), NR_KAISERTABLE); } else @@ -192,7 +205,7 @@ static int kaiser_add_user_map(const voi ret = -EIO; break; } - pte = kaiser_pagetable_walk(address); + pte = kaiser_pagetable_walk(address, flags & _PAGE_USER); if (!pte) { ret = -ENOMEM; break; @@ -319,6 +332,19 @@ void __init kaiser_init(void) kaiser_init_all_pgds(); + /* + * Note that this sets _PAGE_USER and it needs to happen when the + * pagetable hierarchy gets created, i.e., early. Otherwise + * kaiser_pagetable_walk() will encounter initialized PTEs in the + * hierarchy and not set the proper permissions, leading to the + * pagefaults with page-protection violations when trying to read the + * vsyscall page. For example. + */ + if (vsyscall_enabled()) + kaiser_add_user_map_early((void *)VSYSCALL_ADDR, + PAGE_SIZE, + __PAGE_KERNEL_VSYSCALL); + for_each_possible_cpu(cpu) { void *percpu_vaddr = __per_cpu_user_mapped_start + per_cpu_offset(cpu);