From 5006dd0fae6126c149868102c100cd90a20ef2e3 Mon Sep 17 00:00:00 2001 From: Kyle McMartin Date: Mon, 29 Mar 2010 23:20:18 -0400 Subject: execshield cebbert@redhat.com: added fix for bz#220892 diff --git a/arch/x86/include/asm/desc.h b/arch/x86/include/asm/desc.h index 617bd56..526248d 100644 --- a/arch/x86/include/asm/desc.h +++ b/arch/x86/include/asm/desc.h @@ -5,6 +5,7 @@ #include #include #include +#include static inline void fill_ldt(struct desc_struct *desc, const struct user_desc *info) @@ -93,6 +94,9 @@ static inline int desc_empty(const void *ptr) #define load_TLS(t, cpu) native_load_tls(t, cpu) #define set_ldt native_set_ldt +#ifdef CONFIG_X86_32 +#define load_user_cs_desc native_load_user_cs_desc +#endif /*CONFIG_X86_32*/ #define write_ldt_entry(dt, entry, desc) \ native_write_ldt_entry(dt, entry, desc) @@ -392,4 +396,25 @@ static inline void set_system_intr_gate_ist(int n, void *addr, unsigned ist) _set_gate(n, GATE_INTERRUPT, addr, 0x3, ist, __KERNEL_CS); } +#ifdef CONFIG_X86_32 +static inline void set_user_cs(struct desc_struct *desc, unsigned long limit) +{ + limit = (limit - 1) / PAGE_SIZE; + desc->a = limit & 0xffff; + desc->b = (limit & 0xf0000) | 0x00c0fb00; +} + +static inline void native_load_user_cs_desc(int cpu, struct mm_struct *mm) +{ + get_cpu_gdt_table(cpu)[GDT_ENTRY_DEFAULT_USER_CS] = (mm)->context.user_cs; +} + +#define arch_add_exec_range arch_add_exec_range +#define arch_remove_exec_range arch_remove_exec_range +#define arch_flush_exec_range arch_flush_exec_range +extern void arch_add_exec_range(struct mm_struct *mm, unsigned long limit); +extern void arch_remove_exec_range(struct mm_struct *mm, unsigned long limit); +extern void arch_flush_exec_range(struct mm_struct *mm); +#endif /* CONFIG_X86_32 */ + #endif /* _ASM_X86_DESC_H */ diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h index 80a1dee..8314c66 100644 --- a/arch/x86/include/asm/mmu.h +++ b/arch/x86/include/asm/mmu.h @@ -7,12 +7,19 @@ /* * The x86 doesn't have a mmu context, but * we put the segment information here. + * + * exec_limit is used to track the range PROT_EXEC + * mappings span. */ typedef struct { void *ldt; int size; struct mutex lock; void *vdso; +#ifdef CONFIG_X86_32 + struct desc_struct user_cs; + unsigned long exec_limit; +#endif } mm_context_t; #ifdef CONFIG_SMP diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h index 5653f43..55dadb2 100644 --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -289,6 +289,12 @@ static inline void set_ldt(const void *addr, unsigned entries) { PVOP_VCALL2(pv_cpu_ops.set_ldt, addr, entries); } +#ifdef CONFIG_X86_32 +static inline void load_user_cs_desc(unsigned int cpu, struct mm_struct *mm) +{ + PVOP_VCALL2(pv_cpu_ops.load_user_cs_desc, cpu, mm); +} +#endif /*CONFIG_X86_32*/ static inline void store_gdt(struct desc_ptr *dtr) { PVOP_VCALL1(pv_cpu_ops.store_gdt, dtr); diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h index db9ef55..19c2793 100644 --- a/arch/x86/include/asm/paravirt_types.h +++ b/arch/x86/include/asm/paravirt_types.h @@ -118,6 +118,9 @@ struct pv_cpu_ops { void (*store_gdt)(struct desc_ptr *); void (*store_idt)(struct desc_ptr *); void (*set_ldt)(const void *desc, unsigned entries); +#ifdef CONFIG_X86_32 + void (*load_user_cs_desc)(int cpu, struct mm_struct *mm); +#endif unsigned long (*store_tr)(void); void (*load_tls)(struct thread_struct *t, unsigned int cpu); #ifdef CONFIG_X86_64 diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index b753ea5..4893156 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -162,6 +162,9 @@ static inline int hlt_works(int cpu) #define cache_line_size() (boot_cpu_data.x86_cache_alignment) +#define __HAVE_ARCH_ALIGN_STACK +extern unsigned long arch_align_stack(unsigned long sp); + extern void cpu_detect(struct cpuinfo_x86 *c); extern struct pt_regs *idle_regs(struct pt_regs *); diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 4868e4a..6c8d2ca 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -802,6 +802,20 @@ static void __cpuinit identify_cpu(struct cpuinfo_x86 *c) /* Filter out anything that depends on CPUID levels we don't have */ filter_cpuid_features(c, true); + /* + * emulation of NX with segment limits unfortunately means + * we have to disable the fast system calls, due to the way that + * sysexit clears the segment limits on return. + * If we have either disabled exec-shield on the boot command line, + * or we have NX, then we don't need to do this. + */ + if (exec_shield != 0) { +#ifdef CONFIG_X86_PAE + if (!test_cpu_cap(c, X86_FEATURE_NX)) +#endif + clear_cpu_cap(c, X86_FEATURE_SEP); + } + /* If the model name is still unset, do table lookup. */ if (!c->x86_model_id[0]) { const char *p; diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index 1db183e..238b97d 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -345,6 +345,9 @@ struct pv_cpu_ops pv_cpu_ops = { .read_tscp = native_read_tscp, .load_tr_desc = native_load_tr_desc, .set_ldt = native_set_ldt, +#ifdef CONFIG_X86_32 + .load_user_cs_desc = native_load_user_cs_desc, +#endif /*CONFIG_X86_32*/ .load_gdt = native_load_gdt, .load_idt = native_load_idt, .store_gdt = native_store_gdt, diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index f6c6266..8ac2589 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -251,7 +251,10 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, void start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) { + int cpu; + set_user_gs(regs, 0); + regs->fs = 0; set_fs(USER_DS); regs->ds = __USER_DS; @@ -260,6 +263,11 @@ start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp) regs->cs = __USER_CS; regs->ip = new_ip; regs->sp = new_sp; + + cpu = get_cpu(); + load_user_cs_desc(cpu, current->mm); + put_cpu(); + /* * Free the old FP and other extended state */ @@ -319,6 +327,9 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) if (preload_fpu) prefetch(next->xstate); + if (next_p->mm) + load_user_cs_desc(cpu, next_p->mm); + /* * Reload esp0. */ @@ -412,3 +423,40 @@ unsigned long get_wchan(struct task_struct *p) return 0; } +static void modify_cs(struct mm_struct *mm, unsigned long limit) +{ + mm->context.exec_limit = limit; + set_user_cs(&mm->context.user_cs, limit); + if (mm == current->mm) { + int cpu; + + cpu = get_cpu(); + load_user_cs_desc(cpu, mm); + put_cpu(); + } +} + +void arch_add_exec_range(struct mm_struct *mm, unsigned long limit) +{ + if (limit > mm->context.exec_limit) + modify_cs(mm, limit); +} + +void arch_remove_exec_range(struct mm_struct *mm, unsigned long old_end) +{ + struct vm_area_struct *vma; + unsigned long limit = PAGE_SIZE; + + if (old_end == mm->context.exec_limit) { + for (vma = mm->mmap; vma; vma = vma->vm_next) + if ((vma->vm_flags & VM_EXEC) && (vma->vm_end > limit)) + limit = vma->vm_end; + modify_cs(mm, limit); + } +} + +void arch_flush_exec_range(struct mm_struct *mm) +{ + mm->context.exec_limit = 0; + set_user_cs(&mm->context.user_cs, 0); +} diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 1168e44..c452918 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -115,6 +115,76 @@ die_if_kernel(const char *str, struct pt_regs *regs, long err) if (!user_mode_vm(regs)) die(str, regs, err); } + +static inline int +__compare_user_cs_desc(const struct desc_struct *desc1, + const struct desc_struct *desc2) +{ + return ((desc1->limit0 != desc2->limit0) || + (desc1->limit != desc2->limit) || + (desc1->base0 != desc2->base0) || + (desc1->base1 != desc2->base1) || + (desc1->base2 != desc2->base2)); +} + +/* + * lazy-check for CS validity on exec-shield binaries: + * + * the original non-exec stack patch was written by + * Solar Designer . Thanks! + */ +static int +check_lazy_exec_limit(int cpu, struct pt_regs *regs, long error_code) +{ + struct desc_struct *desc1, *desc2; + struct vm_area_struct *vma; + unsigned long limit; + + if (current->mm == NULL) + return 0; + + limit = -1UL; + if (current->mm->context.exec_limit != -1UL) { + limit = PAGE_SIZE; + spin_lock(¤t->mm->page_table_lock); + for (vma = current->mm->mmap; vma; vma = vma->vm_next) + if ((vma->vm_flags & VM_EXEC) && (vma->vm_end > limit)) + limit = vma->vm_end; + vma = get_gate_vma(current); + if (vma && (vma->vm_flags & VM_EXEC) && (vma->vm_end > limit)) + limit = vma->vm_end; + spin_unlock(¤t->mm->page_table_lock); + if (limit >= TASK_SIZE) + limit = -1UL; + current->mm->context.exec_limit = limit; + } + set_user_cs(¤t->mm->context.user_cs, limit); + + desc1 = ¤t->mm->context.user_cs; + desc2 = get_cpu_gdt_table(cpu) + GDT_ENTRY_DEFAULT_USER_CS; + + if (__compare_user_cs_desc(desc1, desc2)) { + /* + * The CS was not in sync - reload it and retry the + * instruction. If the instruction still faults then + * we won't hit this branch next time around. + */ + if (print_fatal_signals >= 2) { + printk(KERN_ERR "#GPF fixup (%ld[seg:%lx]) at %08lx, CPU#%d.\n", + error_code, error_code/8, regs->ip, + smp_processor_id()); + printk(KERN_ERR "exec_limit: %08lx, user_cs: %08x/%08x, CPU_cs: %08x/%08x.\n", + current->mm->context.exec_limit, + desc1->a, desc1->b, desc2->a, desc2->b); + } + + load_user_cs_desc(cpu, current->mm); + + return 1; + } + + return 0; +} #endif static void __kprobes @@ -273,6 +343,29 @@ do_general_protection(struct pt_regs *regs, long error_code) if (!user_mode(regs)) goto gp_in_kernel; +#ifdef CONFIG_X86_32 +{ + int cpu; + int ok; + + cpu = get_cpu(); + ok = check_lazy_exec_limit(cpu, regs, error_code); + put_cpu(); + + if (ok) + return; + + if (print_fatal_signals) { + printk(KERN_ERR "#GPF(%ld[seg:%lx]) at %08lx, CPU#%d.\n", + error_code, error_code/8, regs->ip, smp_processor_id()); + printk(KERN_ERR "exec_limit: %08lx, user_cs: %08x/%08x.\n", + current->mm->context.exec_limit, + current->mm->context.user_cs.a, + current->mm->context.user_cs.b); + } +} +#endif /*CONFIG_X86_32*/ + tsk->thread.error_code = error_code; tsk->thread.trap_no = 13; @@ -863,19 +956,37 @@ do_device_not_available(struct pt_regs *regs, long error_code) } #ifdef CONFIG_X86_32 +/* + * The fixup code for errors in iret jumps to here (iret_exc). It loses + * the original trap number and erorr code. The bogus trap 32 and error + * code 0 are what the vanilla kernel delivers via: + * DO_ERROR_INFO(32, SIGSEGV, "iret exception", iret_error, ILL_BADSTK, 0, 1) + * + * NOTE: Because of the final "1" in the macro we need to enable interrupts. + * + * In case of a general protection fault in the iret instruction, we + * need to check for a lazy CS update for exec-shield. + */ dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code) { - siginfo_t info; + int ok; + int cpu; + local_irq_enable(); - info.si_signo = SIGILL; - info.si_errno = 0; - info.si_code = ILL_BADSTK; - info.si_addr = NULL; - if (notify_die(DIE_TRAP, "iret exception", - regs, error_code, 32, SIGILL) == NOTIFY_STOP) - return; - do_trap(32, SIGILL, "iret exception", regs, error_code, &info); + cpu = get_cpu(); + ok = check_lazy_exec_limit(cpu, regs, error_code); + put_cpu(); + + if (!ok && notify_die(DIE_TRAP, "iret exception", regs, + error_code, 32, SIGSEGV) != NOTIFY_STOP) { + siginfo_t info; + info.si_signo = SIGSEGV; + info.si_errno = 0; + info.si_code = ILL_BADSTK; + info.si_addr = 0; + do_trap(32, SIGSEGV, "iret exception", regs, error_code, &info); + } } #endif diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index 1dab519..360f39d 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -124,13 +124,16 @@ static unsigned long mmap_legacy_base(void) */ void arch_pick_mmap_layout(struct mm_struct *mm) { - if (mmap_is_legacy()) { + if (!(2 & exec_shield) && mmap_is_legacy()) { mm->mmap_base = mmap_legacy_base(); mm->get_unmapped_area = arch_get_unmapped_area; mm->unmap_area = arch_unmap_area; } else { mm->mmap_base = mmap_base(); mm->get_unmapped_area = arch_get_unmapped_area_topdown; + if (!(current->personality & READ_IMPLIES_EXEC) + && mmap_is_ia32()) + mm->get_unmapped_exec_area = arch_get_unmapped_exec_area; mm->unmap_area = arch_unmap_area_topdown; } } diff --git a/arch/x86/mm/setup_nx.c b/arch/x86/mm/setup_nx.c index a3250aa..e0d9cce 100644 --- a/arch/x86/mm/setup_nx.c +++ b/arch/x86/mm/setup_nx.c @@ -1,3 +1,4 @@ +#include #include #include #include @@ -23,6 +24,7 @@ static int __init noexec_setup(char *str) disable_nx = 0; } else if (!strncmp(str, "off", 3)) { disable_nx = 1; + exec_shield = 0; } x86_configure_nx(); return 0; @@ -40,6 +42,10 @@ void __cpuinit x86_configure_nx(void) void __init x86_report_nx(void) { if (!cpu_has_nx) { + if (exec_shield) + printk(KERN_INFO "Using x86 segment limits to approximate NX protection\n"); + else + printk(KERN_NOTICE "Notice: NX (Execute Disable) protection " "missing in CPU or disabled in BIOS!\n"); } else { diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 426f3a1..e0286b1 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -6,6 +6,7 @@ #include #include +#include #include #include #include @@ -131,6 +132,12 @@ void smp_invalidate_interrupt(struct pt_regs *regs) union smp_flush_state *f; cpu = smp_processor_id(); + +#ifdef CONFIG_X86_32 + if (current->active_mm) + load_user_cs_desc(cpu, current->active_mm); +#endif + /* * orig_rax contains the negated interrupt vector. * Use that to determine where the sender put the data. diff --git a/arch/x86/vdso/vdso32-setup.c b/arch/x86/vdso/vdso32-setup.c index 02b442e..957bb67 100644 --- a/arch/x86/vdso/vdso32-setup.c +++ b/arch/x86/vdso/vdso32-setup.c @@ -331,7 +331,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) if (compat) addr = VDSO_HIGH_BASE; else { - addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); + addr = get_unmapped_area_prot(NULL, 0, PAGE_SIZE, 0, 0, 1); if (IS_ERR_VALUE(addr)) { ret = addr; goto up_fail; diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index b607239..e426a3f 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -334,6 +334,24 @@ static void xen_set_ldt(const void *addr, unsigned entries) xen_mc_issue(PARAVIRT_LAZY_CPU); } +#ifdef CONFIG_X86_32 +static void xen_load_user_cs_desc(int cpu, struct mm_struct *mm) +{ + void *gdt; + xmaddr_t mgdt; + u64 descriptor; + struct desc_struct user_cs; + + gdt = &get_cpu_gdt_table(cpu)[GDT_ENTRY_DEFAULT_USER_CS]; + mgdt = virt_to_machine(gdt); + + user_cs = mm->context.user_cs; + descriptor = (u64) user_cs.a | ((u64) user_cs.b) << 32; + + HYPERVISOR_update_descriptor(mgdt.maddr, descriptor); +} +#endif /*CONFIG_X86_32*/ + static void xen_load_gdt(const struct desc_ptr *dtr) { unsigned long va = dtr->address; @@ -960,6 +978,9 @@ static const struct pv_cpu_ops xen_cpu_ops __initdata = { .load_tr_desc = paravirt_nop, .set_ldt = xen_set_ldt, +#ifdef CONFIG_X86_32 + .load_user_cs_desc = xen_load_user_cs_desc, +#endif /*CONFIG_X86_32*/ .load_gdt = xen_load_gdt, .load_idt = xen_load_idt, .load_tls = xen_load_tls, diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 535e763..d114af6 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -74,7 +74,7 @@ static struct linux_binfmt elf_format = { .hasvdso = 1 }; -#define BAD_ADDR(x) ((unsigned long)(x) >= TASK_SIZE) +#define BAD_ADDR(x) IS_ERR_VALUE(x) static int set_brk(unsigned long start, unsigned long end) { @@ -701,6 +701,11 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs) break; } + if (current->personality == PER_LINUX && (exec_shield & 2)) { + executable_stack = EXSTACK_DISABLE_X; + current->flags |= PF_RANDOMIZE; + } + /* Some simple consistency checks for the interpreter */ if (elf_interpreter) { retval = -ELIBBAD; @@ -717,6 +722,15 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs) if (retval) goto out_free_dentry; +#ifdef CONFIG_X86_32 + /* + * Turn off the CS limit completely if exec-shield disabled or + * NX active: + */ + if (!exec_shield || executable_stack != EXSTACK_DISABLE_X || (__supported_pte_mask & _PAGE_NX)) + arch_add_exec_range(current->mm, -1); +#endif + /* OK, This is the point of no return */ current->flags &= ~PF_FORKNOEXEC; current->mm->def_flags = def_flags; @@ -724,7 +738,8 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs) /* Do this immediately, since STACK_TOP as used in setup_arg_pages may depend on the personality. */ SET_PERSONALITY(loc->elf_ex); - if (elf_read_implies_exec(loc->elf_ex, executable_stack)) + if (!(exec_shield & 2) && + elf_read_implies_exec(loc->elf_ex, executable_stack)) current->personality |= READ_IMPLIES_EXEC; if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space) @@ -890,7 +905,7 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs) interpreter, &interp_map_addr, load_bias); - if (!IS_ERR((void *)elf_entry)) { + if (!BAD_ADDR(elf_entry)) { /* * load_elf_interp() returns relocation * adjustment diff --git a/include/linux/mm.h b/include/linux/mm.h index e70f21b..44e6d63 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1259,7 +1259,13 @@ extern int install_special_mapping(struct mm_struct *mm, unsigned long addr, unsigned long len, unsigned long flags, struct page **pages); -extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned long, unsigned long, unsigned long); +extern unsigned long get_unmapped_area_prot(struct file *, unsigned long, unsigned long, unsigned long, unsigned long, int); + +static inline unsigned long get_unmapped_area(struct file *file, unsigned long addr, + unsigned long len, unsigned long pgoff, unsigned long flags) +{ + return get_unmapped_area_prot(file, addr, len, pgoff, flags, 0); +} extern unsigned long do_mmap_pgoff(struct file *file, unsigned long addr, unsigned long len, unsigned long prot, diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index b8bb9a6..f478e39 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -227,6 +227,9 @@ struct mm_struct { unsigned long (*get_unmapped_area) (struct file *filp, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags); + unsigned long (*get_unmapped_exec_area) (struct file *filp, + unsigned long addr, unsigned long len, + unsigned long pgoff, unsigned long flags); void (*unmap_area) (struct mm_struct *mm, unsigned long addr); #endif unsigned long mmap_base; /* base of mmap area */ diff --git a/include/linux/resource.h b/include/linux/resource.h index f1e914e..d2aef9a 100644 --- a/include/linux/resource.h +++ b/include/linux/resource.h @@ -53,8 +53,11 @@ struct rlimit { /* * Limit the stack by to some sane default: root can always * increase this limit if needed.. 8MB seems reasonable. + * + * (2MB more to cover randomization effects.) */ -#define _STK_LIM (8*1024*1024) +#define _STK_LIM (10*1024*1024) +#define EXEC_STACK_BIAS (2*1024*1024) /* * GPG2 wants 64kB of mlocked memory, to make sure pass phrases diff --git a/include/linux/sched.h b/include/linux/sched.h index dad7f66..c5a3948 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -102,6 +102,9 @@ struct fs_struct; struct bts_context; struct perf_event_context; +extern int exec_shield; +extern int print_fatal_signals; + /* * List of flags we want to share for kernel threads, * if only because they are not used by them anyway. @@ -390,6 +393,10 @@ extern void arch_pick_mmap_layout(struct mm_struct *mm); extern unsigned long arch_get_unmapped_area(struct file *, unsigned long, unsigned long, unsigned long, unsigned long); + +extern unsigned long +arch_get_unmapped_exec_area(struct file *, unsigned long, unsigned long, + unsigned long, unsigned long); extern unsigned long arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr, unsigned long len, unsigned long pgoff, diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 8686b0f..a4fad81 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -99,6 +99,26 @@ extern int sysctl_nr_open_min, sysctl_nr_open_max; #ifndef CONFIG_MMU extern int sysctl_nr_trim_pages; #endif + +int exec_shield = (1<<0); +/* exec_shield is a bitmask: + * 0: off; vdso at STACK_TOP, 1 page below TASK_SIZE + * (1<<0) 1: on [also on if !=0] + * (1<<1) 2: force noexecstack regardless of PT_GNU_STACK + * The old settings + * (1<<2) 4: vdso just below .text of main (unless too low) + * (1<<3) 8: vdso just below .text of PT_INTERP (unless too low) + * are ignored because the vdso is placed completely randomly + */ + +static int __init setup_exec_shield(char *str) +{ + get_option(&str, &exec_shield); + + return 1; +} +__setup("exec-shield=", setup_exec_shield); + #ifdef CONFIG_BLOCK extern int blk_iopoll_enabled; #endif @@ -400,6 +420,14 @@ static struct ctl_table kern_table[] = { .mode = 0644, .proc_handler = proc_dointvec, }, + { + .procname = "exec-shield", + .data = &exec_shield, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = &proc_dointvec, + }, + #ifdef CONFIG_PROC_SYSCTL { .procname = "tainted", diff --git a/mm/mmap.c b/mm/mmap.c index 75557c6..8173284 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -28,6 +28,7 @@ #include #include #include +#include #include #include @@ -44,6 +45,18 @@ #define arch_rebalance_pgtables(addr, len) (addr) #endif +/* No sane architecture will #define these to anything else */ +#ifndef arch_add_exec_range +#define arch_add_exec_range(mm, limit) do { ; } while (0) +#endif +#ifndef arch_flush_exec_range +#define arch_flush_exec_range(mm) do { ; } while (0) +#endif +#ifndef arch_remove_exec_range +#define arch_remove_exec_range(mm, limit) do { ; } while (0) +#endif + + static void unmap_region(struct mm_struct *mm, struct vm_area_struct *vma, struct vm_area_struct *prev, unsigned long start, unsigned long end); @@ -388,6 +401,9 @@ static inline void { struct vm_area_struct *next; + if (vma->vm_flags & VM_EXEC) + arch_add_exec_range(mm, vma->vm_end); + vma->vm_prev = prev; if (prev) { next = prev->vm_next; @@ -489,6 +504,8 @@ __vma_unlink(struct mm_struct *mm, struct vm_area_struct *vma, rb_erase(&vma->vm_rb, &mm->mm_rb); if (mm->mmap_cache == vma) mm->mmap_cache = prev; + if (vma->vm_flags & VM_EXEC) + arch_remove_exec_range(mm, vma->vm_end); } /* @@ -798,6 +815,8 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm, } else /* cases 2, 5, 7 */ err = vma_adjust(prev, prev->vm_start, end, prev->vm_pgoff, NULL); + if (prev->vm_flags & VM_EXEC) + arch_add_exec_range(mm, prev->vm_end); if (err) return NULL; return prev; @@ -952,7 +971,8 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr, /* Obtain the address to map to. we verify (or select) it and ensure * that it represents a valid section of the address space. */ - addr = get_unmapped_area(file, addr, len, pgoff, flags); + addr = get_unmapped_area_prot(file, addr, len, pgoff, flags, + prot & PROT_EXEC); if (addr & ~PAGE_MASK) return addr; @@ -1504,8 +1524,8 @@ void arch_unmap_area_topdown(struct mm_struct *mm, unsigned long addr) } unsigned long -get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, - unsigned long pgoff, unsigned long flags) +get_unmapped_area_prot(struct file *file, unsigned long addr, unsigned long len, + unsigned long pgoff, unsigned long flags, int exec) { unsigned long (*get_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long); @@ -1518,7 +1538,11 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, if (len > TASK_SIZE) return -ENOMEM; - get_area = current->mm->get_unmapped_area; + if (exec && current->mm->get_unmapped_exec_area) + get_area = current->mm->get_unmapped_exec_area; + else + get_area = current->mm->get_unmapped_area; + if (file && file->f_op && file->f_op->get_unmapped_area) get_area = file->f_op->get_unmapped_area; addr = get_area(file, addr, len, pgoff, flags); @@ -1532,8 +1556,83 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len, return arch_rebalance_pgtables(addr, len); } +EXPORT_SYMBOL(get_unmapped_area_prot); + +static bool should_randomize(void) +{ + return (current->flags & PF_RANDOMIZE) && + !(current->personality & ADDR_NO_RANDOMIZE); +} + +#define SHLIB_BASE 0x00110000 + +unsigned long +arch_get_unmapped_exec_area(struct file *filp, unsigned long addr0, + unsigned long len0, unsigned long pgoff, unsigned long flags) +{ + unsigned long addr = addr0, len = len0; + struct mm_struct *mm = current->mm; + struct vm_area_struct *vma; + unsigned long tmp; + + if (len > TASK_SIZE) + return -ENOMEM; + + if (flags & MAP_FIXED) + return addr; + + if (!addr) + addr = !should_randomize() ? SHLIB_BASE : + randomize_range(SHLIB_BASE, 0x01000000, len); + + if (addr) { + addr = PAGE_ALIGN(addr); + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && + (!vma || addr + len <= vma->vm_start)) + return addr; + } + + addr = SHLIB_BASE; + for (vma = find_vma(mm, addr); ; vma = vma->vm_next) { + /* At this point: (!vma || addr < vma->vm_end). */ + if (TASK_SIZE - len < addr) + return -ENOMEM; + + if (!vma || addr + len <= vma->vm_start) { + /* + * Must not let a PROT_EXEC mapping get into the + * brk area: + */ + if (addr + len > mm->brk) + goto failed; + + /* + * Up until the brk area we randomize addresses + * as much as possible: + */ + if (addr >= 0x01000000 && should_randomize()) { + tmp = randomize_range(0x01000000, + PAGE_ALIGN(max(mm->start_brk, + (unsigned long)0x08000000)), len); + vma = find_vma(mm, tmp); + if (TASK_SIZE - len >= tmp && + (!vma || tmp + len <= vma->vm_start)) + return tmp; + } + /* + * Ok, randomization didnt work out - return + * the result of the linear search: + */ + return addr; + } + addr = vma->vm_end; + } + +failed: + return current->mm->get_unmapped_area(filp, addr0, len0, pgoff, flags); +} -EXPORT_SYMBOL(get_unmapped_area); /* Look up the first VMA which satisfies addr < vm_end, NULL if none. */ struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr) @@ -1608,6 +1707,16 @@ out: return prev ? prev->vm_next : vma; } +static int over_stack_limit(unsigned long sz) +{ + struct rlimit *rlim = current->signal->rlim; + + if (sz < EXEC_STACK_BIAS) + return 0; + return (sz - EXEC_STACK_BIAS) > + ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur); +} + /* * Verify that the stack growth is acceptable and * update accounting. This is shared with both the @@ -1624,7 +1733,7 @@ static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, uns return -ENOMEM; /* Stack limit test */ - if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur)) + if (over_stack_limit(size)) return -ENOMEM; /* mlock limit tests */ @@ -1936,10 +2045,14 @@ static int __split_vma(struct mm_struct * mm, struct vm_area_struct * vma, if (new->vm_ops && new->vm_ops->open) new->vm_ops->open(new); - if (new_below) + if (new_below) { + unsigned long old_end = vma->vm_end; + err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff + ((addr - new->vm_start) >> PAGE_SHIFT), new); - else + if (vma->vm_flags & VM_EXEC) + arch_remove_exec_range(mm, old_end); + } else err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new); /* Success. */ @@ -2223,6 +2336,7 @@ void exit_mmap(struct mm_struct *mm) free_pgtables(tlb, vma, FIRST_USER_ADDRESS, 0); tlb_finish_mmu(tlb, 0, end); + arch_flush_exec_range(mm); /* * Walk the list again, actually closing and freeing it, diff --git a/mm/mprotect.c b/mm/mprotect.c index 8bc969d..3c9b4fc 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -26,9 +26,14 @@ #include #include #include +#include #include #include +#ifndef arch_remove_exec_range +#define arch_remove_exec_range(mm, limit) do { ; } while (0) +#endif + #ifndef pgprot_modify static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot) { @@ -139,7 +144,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, struct mm_struct *mm = vma->vm_mm; unsigned long oldflags = vma->vm_flags; long nrpages = (end - start) >> PAGE_SHIFT; - unsigned long charged = 0; + unsigned long charged = 0, old_end = vma->vm_end; pgoff_t pgoff; int error; int dirty_accountable = 0; @@ -204,6 +209,9 @@ success: dirty_accountable = 1; } + if (oldflags & VM_EXEC) + arch_remove_exec_range(current->mm, old_end); + mmu_notifier_invalidate_range_start(mm, start, end); if (is_vm_hugetlb_page(vma)) hugetlb_change_protection(vma, start, end, vma->vm_page_prot); diff --git a/mm/mremap.c b/mm/mremap.c index e9c75ef..0a5379f 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -488,10 +488,10 @@ unsigned long do_mremap(unsigned long addr, if (vma->vm_flags & VM_MAYSHARE) map_flags |= MAP_SHARED; - new_addr = get_unmapped_area(vma->vm_file, 0, new_len, + new_addr = get_unmapped_area_prot(vma->vm_file, 0, new_len, vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT), - map_flags); + map_flags, vma->vm_flags & VM_EXEC); if (new_addr & ~PAGE_MASK) { ret = new_addr; goto out; -- 1.7.0.1