diff options
author | Andy Lutomirski <luto@kernel.org> | 2017-12-12 18:56:42 +0300 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2017-12-23 23:13:00 +0300 |
commit | 85900ea51577e31b186e523c8f4e068c79ecc7d3 (patch) | |
tree | 76ddd1071d7c34d45920113429de5ee6e9e21eb1 /arch/x86/mm | |
parent | f55f0501cbf65ec41cca5058513031b711730b1d (diff) | |
download | linux-85900ea51577e31b186e523c8f4e068c79ecc7d3.tar.xz |
x86/pti: Map the vsyscall page if needed
Make VSYSCALLs work fully in PTI mode by mapping them properly to the user
space visible page tables.
[ tglx: Hide unused functions (Patch by Arnd Bergmann) ]
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/mm')
-rw-r--r-- | arch/x86/mm/pti.c | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index b1c38ef9fbbb..bce8aea65606 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -38,6 +38,7 @@ #include <asm/cpufeature.h> #include <asm/hypervisor.h> +#include <asm/vsyscall.h> #include <asm/cmdline.h> #include <asm/pti.h> #include <asm/pgtable.h> @@ -223,6 +224,69 @@ static pmd_t *pti_user_pagetable_walk_pmd(unsigned long address) return pmd_offset(pud, address); } +#ifdef CONFIG_X86_VSYSCALL_EMULATION +/* + * Walk the shadow copy of the page tables (optionally) trying to allocate + * page table pages on the way down. Does not support large pages. + * + * Note: this is only used when mapping *new* kernel data into the + * user/shadow page tables. It is never used for userspace data. + * + * Returns a pointer to a PTE on success, or NULL on failure. + */ +static __init pte_t *pti_user_pagetable_walk_pte(unsigned long address) +{ + gfp_t gfp = (GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO); + pmd_t *pmd = pti_user_pagetable_walk_pmd(address); + pte_t *pte; + + /* We can't do anything sensible if we hit a large mapping. */ + if (pmd_large(*pmd)) { + WARN_ON(1); + return NULL; + } + + if (pmd_none(*pmd)) { + unsigned long new_pte_page = __get_free_page(gfp); + if (!new_pte_page) + return NULL; + + if (pmd_none(*pmd)) { + set_pmd(pmd, __pmd(_KERNPG_TABLE | __pa(new_pte_page))); + new_pte_page = 0; + } + if (new_pte_page) + free_page(new_pte_page); + } + + pte = pte_offset_kernel(pmd, address); + if (pte_flags(*pte) & _PAGE_USER) { + WARN_ONCE(1, "attempt to walk to user pte\n"); + return NULL; + } + return pte; +} + +static void __init pti_setup_vsyscall(void) +{ + pte_t *pte, *target_pte; + unsigned int level; + + pte = lookup_address(VSYSCALL_ADDR, &level); + if (!pte || WARN_ON(level != PG_LEVEL_4K) || pte_none(*pte)) + return; + + target_pte = pti_user_pagetable_walk_pte(VSYSCALL_ADDR); + if (WARN_ON(!target_pte)) + return; + + *target_pte = *pte; + set_vsyscall_pgtable_user_bits(kernel_to_user_pgdp(swapper_pg_dir)); +} +#else +static void __init pti_setup_vsyscall(void) { } +#endif + static void __init pti_clone_pmds(unsigned long start, unsigned long end, pmdval_t clear) { @@ -319,4 +383,5 @@ void __init pti_init(void) pti_clone_user_shared(); pti_clone_entry_text(); pti_setup_espfix64(); + pti_setup_vsyscall(); } |