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![Borislav Petkov](/assets/img/avatar_default.png)
Using static_cpu_has() is pointless on those paths, convert them to the boot_cpu_has() variant. No functional changes. Reported-by: Nadav Amit <nadav.amit@gmail.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Rik van Riel <riel@surriel.com> Reviewed-by: Juergen Gross <jgross@suse.com> # for paravirt Cc: Aubrey Li <aubrey.li@intel.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jann Horn <jannh@google.com> Cc: Joerg Roedel <jroedel@suse.de> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Thomas Lendacky <Thomas.Lendacky@amd.com> Cc: linux-edac@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tony Luck <tony.luck@intel.com> Cc: virtualization@lists.linux-foundation.org Cc: x86@kernel.org Link: https://lkml.kernel.org/r/20190330112022.28888-3-bp@alien8.de
582 lines
14 KiB
C
582 lines
14 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 1992 Krishna Balasubramanian and Linus Torvalds
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* Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
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* Copyright (C) 2002 Andi Kleen
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*
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* This handles calls from both 32bit and 64bit mode.
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*
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* Lock order:
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* contex.ldt_usr_sem
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* mmap_sem
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* context.lock
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*/
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#include <linux/errno.h>
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#include <linux/gfp.h>
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#include <linux/sched.h>
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#include <linux/string.h>
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#include <linux/mm.h>
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#include <linux/smp.h>
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#include <linux/syscalls.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/uaccess.h>
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#include <asm/ldt.h>
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#include <asm/tlb.h>
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#include <asm/desc.h>
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#include <asm/mmu_context.h>
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#include <asm/syscalls.h>
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static void refresh_ldt_segments(void)
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{
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#ifdef CONFIG_X86_64
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unsigned short sel;
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/*
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* Make sure that the cached DS and ES descriptors match the updated
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* LDT.
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*/
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savesegment(ds, sel);
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if ((sel & SEGMENT_TI_MASK) == SEGMENT_LDT)
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loadsegment(ds, sel);
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savesegment(es, sel);
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if ((sel & SEGMENT_TI_MASK) == SEGMENT_LDT)
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loadsegment(es, sel);
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#endif
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}
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/* context.lock is held by the task which issued the smp function call */
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static void flush_ldt(void *__mm)
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{
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struct mm_struct *mm = __mm;
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if (this_cpu_read(cpu_tlbstate.loaded_mm) != mm)
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return;
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load_mm_ldt(mm);
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refresh_ldt_segments();
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}
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/* The caller must call finalize_ldt_struct on the result. LDT starts zeroed. */
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static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries)
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{
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struct ldt_struct *new_ldt;
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unsigned int alloc_size;
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if (num_entries > LDT_ENTRIES)
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return NULL;
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new_ldt = kmalloc(sizeof(struct ldt_struct), GFP_KERNEL);
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if (!new_ldt)
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return NULL;
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BUILD_BUG_ON(LDT_ENTRY_SIZE != sizeof(struct desc_struct));
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alloc_size = num_entries * LDT_ENTRY_SIZE;
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/*
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* Xen is very picky: it requires a page-aligned LDT that has no
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* trailing nonzero bytes in any page that contains LDT descriptors.
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* Keep it simple: zero the whole allocation and never allocate less
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* than PAGE_SIZE.
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*/
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if (alloc_size > PAGE_SIZE)
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new_ldt->entries = vzalloc(alloc_size);
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else
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new_ldt->entries = (void *)get_zeroed_page(GFP_KERNEL);
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if (!new_ldt->entries) {
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kfree(new_ldt);
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return NULL;
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}
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/* The new LDT isn't aliased for PTI yet. */
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new_ldt->slot = -1;
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new_ldt->nr_entries = num_entries;
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return new_ldt;
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}
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#ifdef CONFIG_PAGE_TABLE_ISOLATION
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static void do_sanity_check(struct mm_struct *mm,
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bool had_kernel_mapping,
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bool had_user_mapping)
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{
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if (mm->context.ldt) {
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/*
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* We already had an LDT. The top-level entry should already
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* have been allocated and synchronized with the usermode
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* tables.
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*/
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WARN_ON(!had_kernel_mapping);
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if (boot_cpu_has(X86_FEATURE_PTI))
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WARN_ON(!had_user_mapping);
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} else {
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/*
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* This is the first time we're mapping an LDT for this process.
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* Sync the pgd to the usermode tables.
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*/
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WARN_ON(had_kernel_mapping);
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if (boot_cpu_has(X86_FEATURE_PTI))
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WARN_ON(had_user_mapping);
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}
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}
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#ifdef CONFIG_X86_PAE
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static pmd_t *pgd_to_pmd_walk(pgd_t *pgd, unsigned long va)
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{
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p4d_t *p4d;
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pud_t *pud;
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if (pgd->pgd == 0)
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return NULL;
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p4d = p4d_offset(pgd, va);
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if (p4d_none(*p4d))
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return NULL;
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pud = pud_offset(p4d, va);
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if (pud_none(*pud))
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return NULL;
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return pmd_offset(pud, va);
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}
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static void map_ldt_struct_to_user(struct mm_struct *mm)
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{
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pgd_t *k_pgd = pgd_offset(mm, LDT_BASE_ADDR);
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pgd_t *u_pgd = kernel_to_user_pgdp(k_pgd);
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pmd_t *k_pmd, *u_pmd;
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k_pmd = pgd_to_pmd_walk(k_pgd, LDT_BASE_ADDR);
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u_pmd = pgd_to_pmd_walk(u_pgd, LDT_BASE_ADDR);
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if (boot_cpu_has(X86_FEATURE_PTI) && !mm->context.ldt)
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set_pmd(u_pmd, *k_pmd);
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}
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static void sanity_check_ldt_mapping(struct mm_struct *mm)
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{
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pgd_t *k_pgd = pgd_offset(mm, LDT_BASE_ADDR);
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pgd_t *u_pgd = kernel_to_user_pgdp(k_pgd);
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bool had_kernel, had_user;
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pmd_t *k_pmd, *u_pmd;
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k_pmd = pgd_to_pmd_walk(k_pgd, LDT_BASE_ADDR);
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u_pmd = pgd_to_pmd_walk(u_pgd, LDT_BASE_ADDR);
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had_kernel = (k_pmd->pmd != 0);
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had_user = (u_pmd->pmd != 0);
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do_sanity_check(mm, had_kernel, had_user);
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}
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#else /* !CONFIG_X86_PAE */
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static void map_ldt_struct_to_user(struct mm_struct *mm)
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{
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pgd_t *pgd = pgd_offset(mm, LDT_BASE_ADDR);
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if (boot_cpu_has(X86_FEATURE_PTI) && !mm->context.ldt)
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set_pgd(kernel_to_user_pgdp(pgd), *pgd);
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}
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static void sanity_check_ldt_mapping(struct mm_struct *mm)
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{
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pgd_t *pgd = pgd_offset(mm, LDT_BASE_ADDR);
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bool had_kernel = (pgd->pgd != 0);
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bool had_user = (kernel_to_user_pgdp(pgd)->pgd != 0);
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do_sanity_check(mm, had_kernel, had_user);
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}
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#endif /* CONFIG_X86_PAE */
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/*
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* If PTI is enabled, this maps the LDT into the kernelmode and
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* usermode tables for the given mm.
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*/
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static int
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map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot)
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{
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unsigned long va;
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bool is_vmalloc;
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spinlock_t *ptl;
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int i, nr_pages;
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if (!boot_cpu_has(X86_FEATURE_PTI))
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return 0;
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/*
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* Any given ldt_struct should have map_ldt_struct() called at most
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* once.
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*/
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WARN_ON(ldt->slot != -1);
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/* Check if the current mappings are sane */
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sanity_check_ldt_mapping(mm);
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is_vmalloc = is_vmalloc_addr(ldt->entries);
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nr_pages = DIV_ROUND_UP(ldt->nr_entries * LDT_ENTRY_SIZE, PAGE_SIZE);
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for (i = 0; i < nr_pages; i++) {
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unsigned long offset = i << PAGE_SHIFT;
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const void *src = (char *)ldt->entries + offset;
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unsigned long pfn;
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pgprot_t pte_prot;
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pte_t pte, *ptep;
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va = (unsigned long)ldt_slot_va(slot) + offset;
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pfn = is_vmalloc ? vmalloc_to_pfn(src) :
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page_to_pfn(virt_to_page(src));
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/*
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* Treat the PTI LDT range as a *userspace* range.
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* get_locked_pte() will allocate all needed pagetables
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* and account for them in this mm.
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*/
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ptep = get_locked_pte(mm, va, &ptl);
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if (!ptep)
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return -ENOMEM;
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/*
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* Map it RO so the easy to find address is not a primary
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* target via some kernel interface which misses a
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* permission check.
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*/
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pte_prot = __pgprot(__PAGE_KERNEL_RO & ~_PAGE_GLOBAL);
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/* Filter out unsuppored __PAGE_KERNEL* bits: */
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pgprot_val(pte_prot) &= __supported_pte_mask;
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pte = pfn_pte(pfn, pte_prot);
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set_pte_at(mm, va, ptep, pte);
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pte_unmap_unlock(ptep, ptl);
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}
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/* Propagate LDT mapping to the user page-table */
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map_ldt_struct_to_user(mm);
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ldt->slot = slot;
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return 0;
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}
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static void unmap_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt)
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{
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unsigned long va;
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int i, nr_pages;
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if (!ldt)
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return;
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/* LDT map/unmap is only required for PTI */
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if (!boot_cpu_has(X86_FEATURE_PTI))
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return;
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nr_pages = DIV_ROUND_UP(ldt->nr_entries * LDT_ENTRY_SIZE, PAGE_SIZE);
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for (i = 0; i < nr_pages; i++) {
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unsigned long offset = i << PAGE_SHIFT;
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spinlock_t *ptl;
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pte_t *ptep;
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va = (unsigned long)ldt_slot_va(ldt->slot) + offset;
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ptep = get_locked_pte(mm, va, &ptl);
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pte_clear(mm, va, ptep);
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pte_unmap_unlock(ptep, ptl);
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}
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va = (unsigned long)ldt_slot_va(ldt->slot);
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flush_tlb_mm_range(mm, va, va + nr_pages * PAGE_SIZE, PAGE_SHIFT, false);
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}
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#else /* !CONFIG_PAGE_TABLE_ISOLATION */
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static int
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map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot)
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{
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return 0;
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}
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static void unmap_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt)
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{
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}
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#endif /* CONFIG_PAGE_TABLE_ISOLATION */
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static void free_ldt_pgtables(struct mm_struct *mm)
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{
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#ifdef CONFIG_PAGE_TABLE_ISOLATION
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struct mmu_gather tlb;
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unsigned long start = LDT_BASE_ADDR;
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unsigned long end = LDT_END_ADDR;
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if (!boot_cpu_has(X86_FEATURE_PTI))
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return;
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tlb_gather_mmu(&tlb, mm, start, end);
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free_pgd_range(&tlb, start, end, start, end);
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tlb_finish_mmu(&tlb, start, end);
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#endif
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}
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/* After calling this, the LDT is immutable. */
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static void finalize_ldt_struct(struct ldt_struct *ldt)
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{
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paravirt_alloc_ldt(ldt->entries, ldt->nr_entries);
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}
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static void install_ldt(struct mm_struct *mm, struct ldt_struct *ldt)
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{
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mutex_lock(&mm->context.lock);
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/* Synchronizes with READ_ONCE in load_mm_ldt. */
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smp_store_release(&mm->context.ldt, ldt);
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/* Activate the LDT for all CPUs using currents mm. */
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on_each_cpu_mask(mm_cpumask(mm), flush_ldt, mm, true);
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mutex_unlock(&mm->context.lock);
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}
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static void free_ldt_struct(struct ldt_struct *ldt)
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{
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if (likely(!ldt))
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return;
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paravirt_free_ldt(ldt->entries, ldt->nr_entries);
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if (ldt->nr_entries * LDT_ENTRY_SIZE > PAGE_SIZE)
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vfree_atomic(ldt->entries);
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else
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free_page((unsigned long)ldt->entries);
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kfree(ldt);
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}
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/*
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* Called on fork from arch_dup_mmap(). Just copy the current LDT state,
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* the new task is not running, so nothing can be installed.
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*/
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int ldt_dup_context(struct mm_struct *old_mm, struct mm_struct *mm)
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{
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struct ldt_struct *new_ldt;
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int retval = 0;
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if (!old_mm)
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return 0;
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mutex_lock(&old_mm->context.lock);
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if (!old_mm->context.ldt)
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goto out_unlock;
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new_ldt = alloc_ldt_struct(old_mm->context.ldt->nr_entries);
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if (!new_ldt) {
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retval = -ENOMEM;
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goto out_unlock;
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}
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memcpy(new_ldt->entries, old_mm->context.ldt->entries,
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new_ldt->nr_entries * LDT_ENTRY_SIZE);
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finalize_ldt_struct(new_ldt);
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retval = map_ldt_struct(mm, new_ldt, 0);
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if (retval) {
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free_ldt_pgtables(mm);
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free_ldt_struct(new_ldt);
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goto out_unlock;
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}
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mm->context.ldt = new_ldt;
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out_unlock:
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mutex_unlock(&old_mm->context.lock);
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return retval;
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}
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/*
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* No need to lock the MM as we are the last user
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*
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* 64bit: Don't touch the LDT register - we're already in the next thread.
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*/
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void destroy_context_ldt(struct mm_struct *mm)
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{
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free_ldt_struct(mm->context.ldt);
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mm->context.ldt = NULL;
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}
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void ldt_arch_exit_mmap(struct mm_struct *mm)
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{
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free_ldt_pgtables(mm);
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}
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static int read_ldt(void __user *ptr, unsigned long bytecount)
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{
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struct mm_struct *mm = current->mm;
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unsigned long entries_size;
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int retval;
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down_read(&mm->context.ldt_usr_sem);
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if (!mm->context.ldt) {
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retval = 0;
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goto out_unlock;
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}
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if (bytecount > LDT_ENTRY_SIZE * LDT_ENTRIES)
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bytecount = LDT_ENTRY_SIZE * LDT_ENTRIES;
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entries_size = mm->context.ldt->nr_entries * LDT_ENTRY_SIZE;
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if (entries_size > bytecount)
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entries_size = bytecount;
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if (copy_to_user(ptr, mm->context.ldt->entries, entries_size)) {
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retval = -EFAULT;
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goto out_unlock;
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}
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|
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if (entries_size != bytecount) {
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/* Zero-fill the rest and pretend we read bytecount bytes. */
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if (clear_user(ptr + entries_size, bytecount - entries_size)) {
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retval = -EFAULT;
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goto out_unlock;
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}
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}
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retval = bytecount;
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out_unlock:
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up_read(&mm->context.ldt_usr_sem);
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return retval;
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}
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static int read_default_ldt(void __user *ptr, unsigned long bytecount)
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{
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/* CHECKME: Can we use _one_ random number ? */
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#ifdef CONFIG_X86_32
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unsigned long size = 5 * sizeof(struct desc_struct);
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#else
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unsigned long size = 128;
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#endif
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if (bytecount > size)
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bytecount = size;
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if (clear_user(ptr, bytecount))
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return -EFAULT;
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return bytecount;
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}
|
|
|
|
static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode)
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{
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struct mm_struct *mm = current->mm;
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struct ldt_struct *new_ldt, *old_ldt;
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unsigned int old_nr_entries, new_nr_entries;
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struct user_desc ldt_info;
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struct desc_struct ldt;
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int error;
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error = -EINVAL;
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if (bytecount != sizeof(ldt_info))
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goto out;
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error = -EFAULT;
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if (copy_from_user(&ldt_info, ptr, sizeof(ldt_info)))
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goto out;
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error = -EINVAL;
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if (ldt_info.entry_number >= LDT_ENTRIES)
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goto out;
|
|
if (ldt_info.contents == 3) {
|
|
if (oldmode)
|
|
goto out;
|
|
if (ldt_info.seg_not_present == 0)
|
|
goto out;
|
|
}
|
|
|
|
if ((oldmode && !ldt_info.base_addr && !ldt_info.limit) ||
|
|
LDT_empty(&ldt_info)) {
|
|
/* The user wants to clear the entry. */
|
|
memset(&ldt, 0, sizeof(ldt));
|
|
} else {
|
|
if (!IS_ENABLED(CONFIG_X86_16BIT) && !ldt_info.seg_32bit) {
|
|
error = -EINVAL;
|
|
goto out;
|
|
}
|
|
|
|
fill_ldt(&ldt, &ldt_info);
|
|
if (oldmode)
|
|
ldt.avl = 0;
|
|
}
|
|
|
|
if (down_write_killable(&mm->context.ldt_usr_sem))
|
|
return -EINTR;
|
|
|
|
old_ldt = mm->context.ldt;
|
|
old_nr_entries = old_ldt ? old_ldt->nr_entries : 0;
|
|
new_nr_entries = max(ldt_info.entry_number + 1, old_nr_entries);
|
|
|
|
error = -ENOMEM;
|
|
new_ldt = alloc_ldt_struct(new_nr_entries);
|
|
if (!new_ldt)
|
|
goto out_unlock;
|
|
|
|
if (old_ldt)
|
|
memcpy(new_ldt->entries, old_ldt->entries, old_nr_entries * LDT_ENTRY_SIZE);
|
|
|
|
new_ldt->entries[ldt_info.entry_number] = ldt;
|
|
finalize_ldt_struct(new_ldt);
|
|
|
|
/*
|
|
* If we are using PTI, map the new LDT into the userspace pagetables.
|
|
* If there is already an LDT, use the other slot so that other CPUs
|
|
* will continue to use the old LDT until install_ldt() switches
|
|
* them over to the new LDT.
|
|
*/
|
|
error = map_ldt_struct(mm, new_ldt, old_ldt ? !old_ldt->slot : 0);
|
|
if (error) {
|
|
/*
|
|
* This only can fail for the first LDT setup. If an LDT is
|
|
* already installed then the PTE page is already
|
|
* populated. Mop up a half populated page table.
|
|
*/
|
|
if (!WARN_ON_ONCE(old_ldt))
|
|
free_ldt_pgtables(mm);
|
|
free_ldt_struct(new_ldt);
|
|
goto out_unlock;
|
|
}
|
|
|
|
install_ldt(mm, new_ldt);
|
|
unmap_ldt_struct(mm, old_ldt);
|
|
free_ldt_struct(old_ldt);
|
|
error = 0;
|
|
|
|
out_unlock:
|
|
up_write(&mm->context.ldt_usr_sem);
|
|
out:
|
|
return error;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(modify_ldt, int , func , void __user * , ptr ,
|
|
unsigned long , bytecount)
|
|
{
|
|
int ret = -ENOSYS;
|
|
|
|
switch (func) {
|
|
case 0:
|
|
ret = read_ldt(ptr, bytecount);
|
|
break;
|
|
case 1:
|
|
ret = write_ldt(ptr, bytecount, 1);
|
|
break;
|
|
case 2:
|
|
ret = read_default_ldt(ptr, bytecount);
|
|
break;
|
|
case 0x11:
|
|
ret = write_ldt(ptr, bytecount, 0);
|
|
break;
|
|
}
|
|
/*
|
|
* The SYSCALL_DEFINE() macros give us an 'unsigned long'
|
|
* return type, but tht ABI for sys_modify_ldt() expects
|
|
* 'int'. This cast gives us an int-sized value in %rax
|
|
* for the return code. The 'unsigned' is necessary so
|
|
* the compiler does not try to sign-extend the negative
|
|
* return codes into the high half of the register when
|
|
* taking the value from int->long.
|
|
*/
|
|
return (unsigned int)ret;
|
|
}
|