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 --- include/asm-i386/elf.h | 53 +++++++++++++++++++++++++++++++----------- include/asm-i386/fixmap.h | 10 +------- include/asm-i386/mmu.h | 1 + include/asm-i386/page.h | 3 +++ include/asm-i386/thread_info.h | 1 + include/asm-i386/unwind.h | 4 ++-- include/linux/mm.h | 2 ++ include/linux/sysctl.h | 1 + 8 files changed, 51 insertions(+), 24 deletions(-) (limited to 'include') diff --git a/include/asm-i386/elf.h b/include/asm-i386/elf.h index 4153d80e4d2..1eac92cb5b1 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 f7e068f4d2f..a48cc3f7ccc 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 f431a0b86d4..8358dd3df7a 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 e3a552fa553..f5bf544c729 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 ff1e2b1a7c8..2833fa2c0dd 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 d480f2e3821..69f0f1df672 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 a929ea197e4..ff1fa87df8d 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 349ef908a22..bee12a7a057 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? */ }; 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