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authorIngo Molnar <mingo@elte.hu>2006-06-27 02:53:50 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-27 17:32:38 -0700
commite6e5494cb23d1933735ee47cc674ffe1c4afed6f (patch)
treec8945bb3ae5bec38693d801fb589d22d48d6f8eb /arch/i386/kernel
parentd5fb34261dcd32c9cb3b28121fdc46308db513a1 (diff)
[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 <mingo@elte.hu> Signed-off-by: Arjan van de Ven <arjan@infradead.org> Cc: Gerd Hoffmann <kraxel@suse.de> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Zachary Amsden <zach@vmware.com> Cc: Andi Kleen <ak@muc.de> Cc: Jan Beulich <jbeulich@novell.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch/i386/kernel')
-rw-r--r--arch/i386/kernel/asm-offsets.c4
-rw-r--r--arch/i386/kernel/entry.S7
-rw-r--r--arch/i386/kernel/signal.c4
-rw-r--r--arch/i386/kernel/sysenter.c128
-rw-r--r--arch/i386/kernel/vsyscall-sysenter.S4
-rw-r--r--arch/i386/kernel/vsyscall.lds.S4
6 files changed, 139 insertions, 12 deletions
diff --git a/arch/i386/kernel/asm-offsets.c b/arch/i386/kernel/asm-offsets.c
index 1c3a809e642..c80271f8f08 100644
--- a/arch/i386/kernel/asm-offsets.c
+++ b/arch/i386/kernel/asm-offsets.c
@@ -14,6 +14,7 @@
#include <asm/fixmap.h>
#include <asm/processor.h>
#include <asm/thread_info.h>
+#include <asm/elf.h>
#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 e8d2630fd19..fbdb933251b 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 5c352c3a9e7..43002cfb40c 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 0bada1870bd..c60419dee01 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 <linux/gfp.h>
#include <linux/string.h>
#include <linux/elf.h>
+#include <linux/mm.h>
+#include <linux/module.h>
#include <asm/cpufeature.h>
#include <asm/msr.h>
#include <asm/pgtable.h>
#include <asm/unistd.h>
+/*
+ * 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 3b62baa6a37..1a36d26e15e 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 98699ca6e52..e26975fc68b 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