From e6e5494cb23d1933735ee47cc674ffe1c4afed6f Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Tue, 27 Jun 2006 02:53:50 -0700 Subject: [PATCH] vdso: randomize the i386 vDSO by moving it into a vma Move the i386 VDSO down into a vma and thus randomize it. Besides the security implications, this feature also helps debuggers, which can COW a vma-backed VDSO just like a normal DSO and can thus do single-stepping and other debugging features. It's good for hypervisors (Xen, VMWare) too, which typically live in the same high-mapped address space as the VDSO, hence whenever the VDSO is used, they get lots of guest pagefaults and have to fix such guest accesses up - which slows things down instead of speeding things up (the primary purpose of the VDSO). There's a new CONFIG_COMPAT_VDSO (default=y) option, which provides support for older glibcs that still rely on a prelinked high-mapped VDSO. Newer distributions (using glibc 2.3.3 or later) can turn this option off. Turning it off is also recommended for security reasons: attackers cannot use the predictable high-mapped VDSO page as syscall trampoline anymore. There is a new vdso=[0|1] boot option as well, and a runtime /proc/sys/vm/vdso_enabled sysctl switch, that allows the VDSO to be turned on/off. (This version of the VDSO-randomization patch also has working ELF coredumping, the previous patch crashed in the coredumping code.) This code is a combined work of the exec-shield VDSO randomization code and Gerd Hoffmann's hypervisor-centric VDSO patch. Rusty Russell started this patch and i completed it. [akpm@osdl.org: cleanups] [akpm@osdl.org: compile fix] [akpm@osdl.org: compile fix 2] [akpm@osdl.org: compile fix 3] [akpm@osdl.org: revernt MAXMEM change] Signed-off-by: Ingo Molnar Signed-off-by: Arjan van de Ven Cc: Gerd Hoffmann Cc: Rusty Russell Cc: Zachary Amsden Cc: Andi Kleen Cc: Jan Beulich Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 2e352a6..0d189c9 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1669,6 +1669,10 @@ running once the system is up. usbhid.mousepoll= [USBHID] The interval which mice are to be polled at. + vdso= [IA-32] + vdso=1: enable VDSO (default) + vdso=0: disable VDSO mapping + video= [FB] Frame buffer configuration See Documentation/fb/modedb.txt. diff --git a/arch/i386/Kconfig b/arch/i386/Kconfig index 6662f8c..3bb221d 100644 --- a/arch/i386/Kconfig +++ b/arch/i386/Kconfig @@ -780,6 +780,17 @@ config HOTPLUG_CPU enable suspend on SMP systems. CPUs can be controlled through /sys/devices/system/cpu. +config COMPAT_VDSO + bool "Compat VDSO support" + default y + help + Map the VDSO to the predictable old-style address too. + ---help--- + Say N here if you are running a sufficiently recent glibc + version (2.3.3 or later), to remove the high-mapped + VDSO mapping and to exclusively use the randomized VDSO. + + If unsure, say Y. endmenu diff --git a/arch/i386/kernel/asm-offsets.c b/arch/i386/kernel/asm-offsets.c index 1c3a809..c80271f 100644 --- a/arch/i386/kernel/asm-offsets.c +++ b/arch/i386/kernel/asm-offsets.c @@ -14,6 +14,7 @@ #include #include #include +#include #define DEFINE(sym, val) \ asm volatile("\n->" #sym " %0 " #val : : "i" (val)) @@ -54,6 +55,7 @@ void foo(void) OFFSET(TI_preempt_count, thread_info, preempt_count); OFFSET(TI_addr_limit, thread_info, addr_limit); OFFSET(TI_restart_block, thread_info, restart_block); + OFFSET(TI_sysenter_return, thread_info, sysenter_return); BLANK(); OFFSET(EXEC_DOMAIN_handler, exec_domain, handler); @@ -69,7 +71,7 @@ void foo(void) sizeof(struct tss_struct)); DEFINE(PAGE_SIZE_asm, PAGE_SIZE); - DEFINE(VSYSCALL_BASE, __fix_to_virt(FIX_VSYSCALL)); + DEFINE(VDSO_PRELINK, VDSO_PRELINK); OFFSET(crypto_tfm_ctx_offset, crypto_tfm, __crt_ctx); } diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S index e8d2630..fbdb933 100644 --- a/arch/i386/kernel/entry.S +++ b/arch/i386/kernel/entry.S @@ -270,7 +270,12 @@ sysenter_past_esp: pushl $(__USER_CS) CFI_ADJUST_CFA_OFFSET 4 /*CFI_REL_OFFSET cs, 0*/ - pushl $SYSENTER_RETURN + /* + * Push current_thread_info()->sysenter_return to the stack. + * A tiny bit of offset fixup is necessary - 4*4 means the 4 words + * pushed above; +8 corresponds to copy_thread's esp0 setting. + */ + pushl (TI_sysenter_return-THREAD_SIZE+8+4*4)(%esp) CFI_ADJUST_CFA_OFFSET 4 CFI_REL_OFFSET eip, 0 diff --git a/arch/i386/kernel/signal.c b/arch/i386/kernel/signal.c index 5c352c3..43002cf 100644 --- a/arch/i386/kernel/signal.c +++ b/arch/i386/kernel/signal.c @@ -351,7 +351,7 @@ static int setup_frame(int sig, struct k_sigaction *ka, goto give_sigsegv; } - restorer = &__kernel_sigreturn; + restorer = (void *)VDSO_SYM(&__kernel_sigreturn); if (ka->sa.sa_flags & SA_RESTORER) restorer = ka->sa.sa_restorer; @@ -447,7 +447,7 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info, goto give_sigsegv; /* Set up to return from userspace. */ - restorer = &__kernel_rt_sigreturn; + restorer = (void *)VDSO_SYM(&__kernel_rt_sigreturn); if (ka->sa.sa_flags & SA_RESTORER) restorer = ka->sa.sa_restorer; err |= __put_user(restorer, &frame->pretcode); diff --git a/arch/i386/kernel/sysenter.c b/arch/i386/kernel/sysenter.c index 0bada18..c60419de 100644 --- a/arch/i386/kernel/sysenter.c +++ b/arch/i386/kernel/sysenter.c @@ -2,6 +2,8 @@ * linux/arch/i386/kernel/sysenter.c * * (C) Copyright 2002 Linus Torvalds + * Portions based on the vdso-randomization code from exec-shield: + * Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar * * This file contains the needed initializations to support sysenter. */ @@ -13,12 +15,31 @@ #include #include #include +#include +#include #include #include #include #include +/* + * Should the kernel map a VDSO page into processes and pass its + * address down to glibc upon exec()? + */ +unsigned int __read_mostly vdso_enabled = 1; + +EXPORT_SYMBOL_GPL(vdso_enabled); + +static int __init vdso_setup(char *s) +{ + vdso_enabled = simple_strtoul(s, NULL, 0); + + return 1; +} + +__setup("vdso=", vdso_setup); + extern asmlinkage void sysenter_entry(void); void enable_sep_cpu(void) @@ -45,23 +66,122 @@ void enable_sep_cpu(void) */ extern const char vsyscall_int80_start, vsyscall_int80_end; extern const char vsyscall_sysenter_start, vsyscall_sysenter_end; +static void *syscall_page; int __init sysenter_setup(void) { - void *page = (void *)get_zeroed_page(GFP_ATOMIC); + syscall_page = (void *)get_zeroed_page(GFP_ATOMIC); - __set_fixmap(FIX_VSYSCALL, __pa(page), PAGE_READONLY_EXEC); +#ifdef CONFIG_COMPAT_VDSO + __set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_READONLY); + printk("Compat vDSO mapped to %08lx.\n", __fix_to_virt(FIX_VDSO)); +#else + /* + * In the non-compat case the ELF coredumping code needs the fixmap: + */ + __set_fixmap(FIX_VDSO, __pa(syscall_page), PAGE_KERNEL_RO); +#endif if (!boot_cpu_has(X86_FEATURE_SEP)) { - memcpy(page, + memcpy(syscall_page, &vsyscall_int80_start, &vsyscall_int80_end - &vsyscall_int80_start); return 0; } - memcpy(page, + memcpy(syscall_page, &vsyscall_sysenter_start, &vsyscall_sysenter_end - &vsyscall_sysenter_start); return 0; } + +static struct page *syscall_nopage(struct vm_area_struct *vma, + unsigned long adr, int *type) +{ + struct page *p = virt_to_page(adr - vma->vm_start + syscall_page); + get_page(p); + return p; +} + +/* Prevent VMA merging */ +static void syscall_vma_close(struct vm_area_struct *vma) +{ +} + +static struct vm_operations_struct syscall_vm_ops = { + .close = syscall_vma_close, + .nopage = syscall_nopage, +}; + +/* Defined in vsyscall-sysenter.S */ +extern void SYSENTER_RETURN; + +/* Setup a VMA at program startup for the vsyscall page */ +int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack) +{ + struct vm_area_struct *vma; + struct mm_struct *mm = current->mm; + unsigned long addr; + int ret; + + down_write(&mm->mmap_sem); + addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); + if (IS_ERR_VALUE(addr)) { + ret = addr; + goto up_fail; + } + + vma = kmem_cache_zalloc(vm_area_cachep, SLAB_KERNEL); + if (!vma) { + ret = -ENOMEM; + goto up_fail; + } + + vma->vm_start = addr; + vma->vm_end = addr + PAGE_SIZE; + /* MAYWRITE to allow gdb to COW and set breakpoints */ + vma->vm_flags = VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC|VM_MAYWRITE; + vma->vm_flags |= mm->def_flags; + vma->vm_page_prot = protection_map[vma->vm_flags & 7]; + vma->vm_ops = &syscall_vm_ops; + vma->vm_mm = mm; + + ret = insert_vm_struct(mm, vma); + if (ret) + goto free_vma; + + current->mm->context.vdso = (void *)addr; + current_thread_info()->sysenter_return = + (void *)VDSO_SYM(&SYSENTER_RETURN); + mm->total_vm++; +up_fail: + up_write(&mm->mmap_sem); + return ret; + +free_vma: + kmem_cache_free(vm_area_cachep, vma); + return ret; +} + +const char *arch_vma_name(struct vm_area_struct *vma) +{ + if (vma->vm_mm && vma->vm_start == (long)vma->vm_mm->context.vdso) + return "[vdso]"; + return NULL; +} + +struct vm_area_struct *get_gate_vma(struct task_struct *tsk) +{ + return NULL; +} + +int in_gate_area(struct task_struct *task, unsigned long addr) +{ + return 0; +} + +int in_gate_area_no_task(unsigned long addr) +{ + return 0; +} diff --git a/arch/i386/kernel/vsyscall-sysenter.S b/arch/i386/kernel/vsyscall-sysenter.S index 3b62baa..1a36d26 100644 --- a/arch/i386/kernel/vsyscall-sysenter.S +++ b/arch/i386/kernel/vsyscall-sysenter.S @@ -42,10 +42,10 @@ __kernel_vsyscall: /* 7: align return point with nop's to make disassembly easier */ .space 7,0x90 - /* 14: System call restart point is here! (SYSENTER_RETURN - 2) */ + /* 14: System call restart point is here! (SYSENTER_RETURN-2) */ jmp .Lenter_kernel /* 16: System call normal return point is here! */ - .globl SYSENTER_RETURN /* Symbol used by entry.S. */ + .globl SYSENTER_RETURN /* Symbol used by sysenter.c */ SYSENTER_RETURN: pop %ebp .Lpop_ebp: diff --git a/arch/i386/kernel/vsyscall.lds.S b/arch/i386/kernel/vsyscall.lds.S index 98699ca..e26975f 100644 --- a/arch/i386/kernel/vsyscall.lds.S +++ b/arch/i386/kernel/vsyscall.lds.S @@ -7,7 +7,7 @@ SECTIONS { - . = VSYSCALL_BASE + SIZEOF_HEADERS; + . = VDSO_PRELINK + SIZEOF_HEADERS; .hash : { *(.hash) } :text .dynsym : { *(.dynsym) } @@ -20,7 +20,7 @@ SECTIONS For the layouts to match, we need to skip more than enough space for the dynamic symbol table et al. If this amount is insufficient, ld -shared will barf. Just increase it here. */ - . = VSYSCALL_BASE + 0x400; + . = VDSO_PRELINK + 0x400; .text : { *(.text) } :text =0x90909090 .note : { *(.note.*) } :text :note diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 0137ec4..0a163a4 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -122,6 +122,11 @@ struct mem_size_stats unsigned long private_dirty; }; +__attribute__((weak)) const char *arch_vma_name(struct vm_area_struct *vma) +{ + return NULL; +} + static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats *mss) { struct proc_maps_private *priv = m->private; @@ -158,22 +163,23 @@ static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats pad_len_spaces(m, len); seq_path(m, file->f_vfsmnt, file->f_dentry, "\n"); } else { - if (mm) { - if (vma->vm_start <= mm->start_brk && + const char *name = arch_vma_name(vma); + if (!name) { + if (mm) { + if (vma->vm_start <= mm->start_brk && vma->vm_end >= mm->brk) { - pad_len_spaces(m, len); - seq_puts(m, "[heap]"); - } else { - if (vma->vm_start <= mm->start_stack && - vma->vm_end >= mm->start_stack) { - - pad_len_spaces(m, len); - seq_puts(m, "[stack]"); + name = "[heap]"; + } else if (vma->vm_start <= mm->start_stack && + vma->vm_end >= mm->start_stack) { + name = "[stack]"; } + } else { + name = "[vdso]"; } - } else { + } + if (name) { pad_len_spaces(m, len); - seq_puts(m, "[vdso]"); + seq_puts(m, name); } } seq_putc(m, '\n'); diff --git a/include/asm-i386/elf.h b/include/asm-i386/elf.h index 4153d80..1eac92c 100644 --- a/include/asm-i386/elf.h +++ b/include/asm-i386/elf.h @@ -10,6 +10,7 @@ #include #include /* for savesegment */ #include +#include #include @@ -129,15 +130,41 @@ extern int dump_task_extended_fpu (struct task_struct *, struct user_fxsr_struct #define ELF_CORE_COPY_FPREGS(tsk, elf_fpregs) dump_task_fpu(tsk, elf_fpregs) #define ELF_CORE_COPY_XFPREGS(tsk, elf_xfpregs) dump_task_extended_fpu(tsk, elf_xfpregs) -#define VSYSCALL_BASE (__fix_to_virt(FIX_VSYSCALL)) -#define VSYSCALL_EHDR ((const struct elfhdr *) VSYSCALL_BASE) -#define VSYSCALL_ENTRY ((unsigned long) &__kernel_vsyscall) +#define VDSO_HIGH_BASE (__fix_to_virt(FIX_VDSO)) +#define VDSO_BASE ((unsigned long)current->mm->context.vdso) + +#ifdef CONFIG_COMPAT_VDSO +# define VDSO_COMPAT_BASE VDSO_HIGH_BASE +# define VDSO_PRELINK VDSO_HIGH_BASE +#else +# define VDSO_COMPAT_BASE VDSO_BASE +# define VDSO_PRELINK 0 +#endif + +#define VDSO_COMPAT_SYM(x) \ + (VDSO_COMPAT_BASE + (unsigned long)(x) - VDSO_PRELINK) + +#define VDSO_SYM(x) \ + (VDSO_BASE + (unsigned long)(x) - VDSO_PRELINK) + +#define VDSO_HIGH_EHDR ((const struct elfhdr *) VDSO_HIGH_BASE) +#define VDSO_EHDR ((const struct elfhdr *) VDSO_COMPAT_BASE) + extern void __kernel_vsyscall; +#define VDSO_ENTRY VDSO_SYM(&__kernel_vsyscall) + +#define ARCH_HAS_SETUP_ADDITIONAL_PAGES +struct linux_binprm; +extern int arch_setup_additional_pages(struct linux_binprm *bprm, + int executable_stack); + +extern unsigned int vdso_enabled; + #define ARCH_DLINFO \ -do { \ - NEW_AUX_ENT(AT_SYSINFO, VSYSCALL_ENTRY); \ - NEW_AUX_ENT(AT_SYSINFO_EHDR, VSYSCALL_BASE); \ +do if (vdso_enabled) { \ + NEW_AUX_ENT(AT_SYSINFO, VDSO_ENTRY); \ + NEW_AUX_ENT(AT_SYSINFO_EHDR, VDSO_COMPAT_BASE); \ } while (0) /* @@ -148,15 +175,15 @@ do { \ * Dumping its extra ELF program headers includes all the other information * a debugger needs to easily find how the vsyscall DSO was being used. */ -#define ELF_CORE_EXTRA_PHDRS (VSYSCALL_EHDR->e_phnum) +#define ELF_CORE_EXTRA_PHDRS (VDSO_HIGH_EHDR->e_phnum) #define ELF_CORE_WRITE_EXTRA_PHDRS \ do { \ const struct elf_phdr *const vsyscall_phdrs = \ - (const struct elf_phdr *) (VSYSCALL_BASE \ - + VSYSCALL_EHDR->e_phoff); \ + (const struct elf_phdr *) (VDSO_HIGH_BASE \ + + VDSO_HIGH_EHDR->e_phoff); \ int i; \ Elf32_Off ofs = 0; \ - for (i = 0; i < VSYSCALL_EHDR->e_phnum; ++i) { \ + for (i = 0; i < VDSO_HIGH_EHDR->e_phnum; ++i) { \ struct elf_phdr phdr = vsyscall_phdrs[i]; \ if (phdr.p_type == PT_LOAD) { \ BUG_ON(ofs != 0); \ @@ -174,10 +201,10 @@ do { \ #define ELF_CORE_WRITE_EXTRA_DATA \ do { \ const struct elf_phdr *const vsyscall_phdrs = \ - (const struct elf_phdr *) (VSYSCALL_BASE \ - + VSYSCALL_EHDR->e_phoff); \ + (const struct elf_phdr *) (VDSO_HIGH_BASE \ + + VDSO_HIGH_EHDR->e_phoff); \ int i; \ - for (i = 0; i < VSYSCALL_EHDR->e_phnum; ++i) { \ + for (i = 0; i < VDSO_HIGH_EHDR->e_phnum; ++i) { \ if (vsyscall_phdrs[i].p_type == PT_LOAD) \ DUMP_WRITE((void *) vsyscall_phdrs[i].p_vaddr, \ PAGE_ALIGN(vsyscall_phdrs[i].p_memsz)); \ diff --git a/include/asm-i386/fixmap.h b/include/asm-i386/fixmap.h index f7e068f..a48cc3f 100644 --- a/include/asm-i386/fixmap.h +++ b/include/asm-i386/fixmap.h @@ -51,7 +51,7 @@ */ enum fixed_addresses { FIX_HOLE, - FIX_VSYSCALL, + FIX_VDSO, #ifdef CONFIG_X86_LOCAL_APIC FIX_APIC_BASE, /* local (CPU) APIC) -- required for SMP or not */ #endif @@ -115,14 +115,6 @@ extern void __set_fixmap (enum fixed_addresses idx, #define __fix_to_virt(x) (FIXADDR_TOP - ((x) << PAGE_SHIFT)) #define __virt_to_fix(x) ((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT) -/* - * This is the range that is readable by user mode, and things - * acting like user mode such as get_user_pages. - */ -#define FIXADDR_USER_START (__fix_to_virt(FIX_VSYSCALL)) -#define FIXADDR_USER_END (FIXADDR_USER_START + PAGE_SIZE) - - extern void __this_fixmap_does_not_exist(void); /* diff --git a/include/asm-i386/mmu.h b/include/asm-i386/mmu.h index f431a0b..8358dd3 100644 --- a/include/asm-i386/mmu.h +++ b/include/asm-i386/mmu.h @@ -12,6 +12,7 @@ typedef struct { int size; struct semaphore sem; void *ldt; + void *vdso; } mm_context_t; #endif diff --git a/include/asm-i386/page.h b/include/asm-i386/page.h index e3a552f..f5bf544 100644 --- a/include/asm-i386/page.h +++ b/include/asm-i386/page.h @@ -96,6 +96,8 @@ typedef struct { unsigned long pgprot; } pgprot_t; #ifndef __ASSEMBLY__ +struct vm_area_struct; + /* * This much address space is reserved for vmalloc() and iomap() * as well as fixmap mappings. @@ -139,6 +141,7 @@ extern int page_is_ram(unsigned long pagenr); #include #include +#define __HAVE_ARCH_GATE_AREA 1 #endif /* __KERNEL__ */ #endif /* _I386_PAGE_H */ diff --git a/include/asm-i386/thread_info.h b/include/asm-i386/thread_info.h index ff1e2b1..2833fa2 100644 --- a/include/asm-i386/thread_info.h +++ b/include/asm-i386/thread_info.h @@ -37,6 +37,7 @@ struct thread_info { 0-0xBFFFFFFF for user-thead 0-0xFFFFFFFF for kernel-thread */ + void *sysenter_return; struct restart_block restart_block; unsigned long previous_esp; /* ESP of the previous stack in case diff --git a/include/asm-i386/unwind.h b/include/asm-i386/unwind.h index d480f2e..69f0f1d 100644 --- a/include/asm-i386/unwind.h +++ b/include/asm-i386/unwind.h @@ -78,8 +78,8 @@ static inline int arch_unw_user_mode(const struct unwind_frame_info *info) return user_mode_vm(&info->regs); #else return info->regs.eip < PAGE_OFFSET - || (info->regs.eip >= __fix_to_virt(FIX_VSYSCALL) - && info->regs.eip < __fix_to_virt(FIX_VSYSCALL) + PAGE_SIZE) + || (info->regs.eip >= __fix_to_virt(FIX_VDSO) + && info->regs.eip < __fix_to_virt(FIX_VDSO) + PAGE_SIZE) || info->regs.esp < PAGE_OFFSET; #endif } diff --git a/include/linux/mm.h b/include/linux/mm.h index a929ea1..ff1fa87 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1065,5 +1065,7 @@ void drop_slab(void); extern int randomize_va_space; #endif +const char *arch_vma_name(struct vm_area_struct *vma); + #endif /* __KERNEL__ */ #endif /* _LINUX_MM_H */ diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index 349ef90..bee12a7 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -189,6 +189,7 @@ enum VM_ZONE_RECLAIM_MODE=31, /* reclaim local zone memory before going off node */ VM_ZONE_RECLAIM_INTERVAL=32, /* time period to wait after reclaim failure */ VM_PANIC_ON_OOM=33, /* panic at out-of-memory */ + VM_VDSO_ENABLED=34, /* map VDSO into new processes? */ }; diff --git a/kernel/sysctl.c b/kernel/sysctl.c index f1a4eb1..f54afed 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -928,6 +928,18 @@ static ctl_table vm_table[] = { .strategy = &sysctl_jiffies, }, #endif +#ifdef CONFIG_X86_32 + { + .ctl_name = VM_VDSO_ENABLED, + .procname = "vdso_enabled", + .data = &vdso_enabled, + .maxlen = sizeof(vdso_enabled), + .mode = 0644, + .proc_handler = &proc_dointvec, + .strategy = &sysctl_intvec, + .extra1 = &zero, + }, +#endif { .ctl_name = 0 } }; -- cgit v0.10.2