From 9bae3197e15dd5e03ce8e237db6fe4486b08a775 Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Wed, 18 Jul 2018 11:41:12 +0200 Subject: [PATCH] x86/ldt: Split out sanity check in map_ldt_struct() This splits out the mapping sanity check and the actual mapping of the LDT to user-space from the map_ldt_struct() function in a way so that it is re-usable for PAE paging. Signed-off-by: Joerg Roedel Signed-off-by: Thomas Gleixner Tested-by: Pavel Machek Cc: "H . Peter Anvin" Cc: linux-mm@kvack.org Cc: Linus Torvalds Cc: Andy Lutomirski Cc: Dave Hansen Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Jiri Kosina Cc: Boris Ostrovsky Cc: Brian Gerst Cc: David Laight Cc: Denys Vlasenko Cc: Eduardo Valentin Cc: Greg KH Cc: Will Deacon Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Cc: Andrea Arcangeli Cc: Waiman Long Cc: "David H . Gutteridge" Cc: joro@8bytes.org Link: https://lkml.kernel.org/r/1531906876-13451-36-git-send-email-joro@8bytes.org --- arch/x86/kernel/ldt.c | 82 ++++++++++++++++++++++++++++++++++++--------------- 1 file changed, 58 insertions(+), 24 deletions(-) diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c index e921b3d494d5..69af9a0d57b7 100644 --- a/arch/x86/kernel/ldt.c +++ b/arch/x86/kernel/ldt.c @@ -100,6 +100,49 @@ static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries) return new_ldt; } +#ifdef CONFIG_PAGE_TABLE_ISOLATION + +static void do_sanity_check(struct mm_struct *mm, + bool had_kernel_mapping, + bool had_user_mapping) +{ + if (mm->context.ldt) { + /* + * We already had an LDT. The top-level entry should already + * have been allocated and synchronized with the usermode + * tables. + */ + WARN_ON(!had_kernel_mapping); + if (static_cpu_has(X86_FEATURE_PTI)) + WARN_ON(!had_user_mapping); + } else { + /* + * This is the first time we're mapping an LDT for this process. + * Sync the pgd to the usermode tables. + */ + WARN_ON(had_kernel_mapping); + if (static_cpu_has(X86_FEATURE_PTI)) + WARN_ON(had_user_mapping); + } +} + +static void map_ldt_struct_to_user(struct mm_struct *mm) +{ + pgd_t *pgd = pgd_offset(mm, LDT_BASE_ADDR); + + if (static_cpu_has(X86_FEATURE_PTI) && !mm->context.ldt) + set_pgd(kernel_to_user_pgdp(pgd), *pgd); +} + +static void sanity_check_ldt_mapping(struct mm_struct *mm) +{ + pgd_t *pgd = pgd_offset(mm, LDT_BASE_ADDR); + bool had_kernel = (pgd->pgd != 0); + bool had_user = (kernel_to_user_pgdp(pgd)->pgd != 0); + + do_sanity_check(mm, had_kernel, had_user); +} + /* * If PTI is enabled, this maps the LDT into the kernelmode and * usermode tables for the given mm. @@ -115,9 +158,8 @@ static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries) static int map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot) { -#ifdef CONFIG_PAGE_TABLE_ISOLATION - bool is_vmalloc, had_top_level_entry; unsigned long va; + bool is_vmalloc; spinlock_t *ptl; pgd_t *pgd; int i; @@ -131,13 +173,15 @@ map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot) */ WARN_ON(ldt->slot != -1); + /* Check if the current mappings are sane */ + sanity_check_ldt_mapping(mm); + /* * Did we already have the top level entry allocated? We can't * use pgd_none() for this because it doens't do anything on * 4-level page table kernels. */ pgd = pgd_offset(mm, LDT_BASE_ADDR); - had_top_level_entry = (pgd->pgd != 0); is_vmalloc = is_vmalloc_addr(ldt->entries); @@ -172,35 +216,25 @@ map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot) pte_unmap_unlock(ptep, ptl); } - if (mm->context.ldt) { - /* - * We already had an LDT. The top-level entry should already - * have been allocated and synchronized with the usermode - * tables. - */ - WARN_ON(!had_top_level_entry); - if (static_cpu_has(X86_FEATURE_PTI)) - WARN_ON(!kernel_to_user_pgdp(pgd)->pgd); - } else { - /* - * This is the first time we're mapping an LDT for this process. - * Sync the pgd to the usermode tables. - */ - WARN_ON(had_top_level_entry); - if (static_cpu_has(X86_FEATURE_PTI)) { - WARN_ON(kernel_to_user_pgdp(pgd)->pgd); - set_pgd(kernel_to_user_pgdp(pgd), *pgd); - } - } + /* Propagate LDT mapping to the user page-table */ + map_ldt_struct_to_user(mm); va = (unsigned long)ldt_slot_va(slot); flush_tlb_mm_range(mm, va, va + LDT_SLOT_STRIDE, 0); ldt->slot = slot; -#endif return 0; } +#else /* !CONFIG_PAGE_TABLE_ISOLATION */ + +static int +map_ldt_struct(struct mm_struct *mm, struct ldt_struct *ldt, int slot) +{ + return 0; +} +#endif /* CONFIG_PAGE_TABLE_ISOLATION */ + static void free_ldt_pgtables(struct mm_struct *mm) { #ifdef CONFIG_PAGE_TABLE_ISOLATION -- 2.11.0