/* * linux/kernel/ptrace.c * * (C) Copyright 1999 Linus Torvalds * * Common interfaces for "ptrace()" which we do not want * to continually duplicate across every architecture. */ #include <linux/capability.h> #include <linux/module.h> #include <linux/sched.h> #include <linux/errno.h> #include <linux/mm.h> #include <linux/highmem.h> #include <linux/pagemap.h> #include <linux/smp_lock.h> #include <linux/ptrace.h> #include <linux/security.h> #include <linux/signal.h> #include <linux/audit.h> #include <linux/pid_namespace.h> #include <linux/syscalls.h> #include <asm/pgtable.h> #include <asm/uaccess.h> /* * ptrace a task: make the debugger its new parent and * move it to the ptrace list. * * Must be called with the tasklist lock write-held. */ void __ptrace_link(struct task_struct *child, struct task_struct *new_parent) { BUG_ON(!list_empty(&child->ptrace_entry)); list_add(&child->ptrace_entry, &new_parent->ptraced); child->parent = new_parent; } /* * Turn a tracing stop into a normal stop now, since with no tracer there * would be no way to wake it up with SIGCONT or SIGKILL. If there was a * signal sent that would resume the child, but didn't because it was in * TASK_TRACED, resume it now. * Requires that irqs be disabled. */ static void ptrace_untrace(struct task_struct *child) { spin_lock(&child->sighand->siglock); if (task_is_traced(child)) { if (child->signal->flags & SIGNAL_STOP_STOPPED) { __set_task_state(child, TASK_STOPPED); } else { signal_wake_up(child, 1); } } spin_unlock(&child->sighand->siglock); } /* * unptrace a task: move it back to its original parent and * remove it from the ptrace list. * * Must be called with the tasklist lock write-held. */ void __ptrace_unlink(struct task_struct *child) { BUG_ON(!child->ptrace); child->ptrace = 0; child->parent = child->real_parent; list_del_init(&child->ptrace_entry); if (task_is_traced(child)) ptrace_untrace(child); } /* * Check that we have indeed attached to the thing.. */ int ptrace_check_attach(struct task_struct *child, int kill) { int ret = -ESRCH; /* * We take the read lock around doing both checks to close a * possible race where someone else was tracing our child and * detached between these two checks. After this locked check, * we are sure that this is our traced child and that can only * be changed by us so it's not changing right after this. */ read_lock(&tasklist_lock); if ((child->ptrace & PT_PTRACED) && child->parent == current) { ret = 0; /* * child->sighand can't be NULL, release_task() * does ptrace_unlink() before __exit_signal(). */ spin_lock_irq(&child->sighand->siglock); if (task_is_stopped(child)) child->state = TASK_TRACED; else if (!task_is_traced(child) && !kill) ret = -ESRCH; spin_unlock_irq(&child->sighand->siglock); } read_unlock(&tasklist_lock); if (!ret && !kill) ret = wait_task_inactive(child, TASK_TRACED) ? 0 : -ESRCH; /* All systems go.. */ return ret; } int __ptrace_may_access(struct task_struct *task, unsigned int mode) { /* May we inspect the given task? * This check is used both for attaching with ptrace * and for allowing access to sensitive information in /proc. * * ptrace_attach denies several cases that /proc allows * because setting up the necessary parent/child relationship * or halting the specified task is impossible. */ int dumpable = 0; /* Don't let security modules deny introspection */ if (task == current) return 0; if (((current->uid != task->euid) || (current->uid != task->suid) || (current->uid != task->uid) || (current->gid != task->egid) || (current->gid != task->sgid) || (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE)) return -EPERM; smp_rmb(); if (task->mm) dumpable = get_dumpable(task->mm); if (!dumpable && !capable(CAP_SYS_PTRACE)) return -EPERM; return security_ptrace_may_access(task, mode); } bool ptrace_may_access(struct task_struct *task, unsigned int mode) { int err; task_lock(task); err = __ptrace_may_access(task, mode); task_unlock(task); return (!err ? true : false); } int ptrace_attach(struct task_struct *task) { int retval; unsigned long flags; audit_ptrace(task); retval = -EPERM; if (same_thread_group(task, current)) goto out; repeat: /* * Nasty, nasty. * * We want to hold both the task-lock and the * tasklist_lock for writing at the same time. * But that's against the rules (tasklist_lock * is taken for reading by interrupts on other * cpu's that may have task_lock). */ task_lock(task); if (!write_trylock_irqsave(&tasklist_lock, flags)) { task_unlock(task); do { cpu_relax(); } while (!write_can_lock(&tasklist_lock)); goto repeat; } if (!task->mm) goto bad; /* the same process cannot be attached many times */ if (task->ptrace & PT_PTRACED) goto bad; retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH); if (retval) goto bad; /* Go */ task->ptrace |= PT_PTRACED; if (capable(CAP_SYS_PTRACE)) task->ptrace |= PT_PTRACE_CAP; __ptrace_link(task, current); send_sig_info(SIGSTOP, SEND_SIG_FORCED, task); bad: write_unlock_irqrestore(&tasklist_lock, flags); task_unlock(task); out: return retval; } static inline void __ptrace_detach(struct task_struct *child, unsigned int data) { child->exit_code = data; /* .. re-parent .. */ __ptrace_unlink(child); /* .. and wake it up. */ if (child->exit_state != EXIT_ZOMBIE) wake_up_process(child); } int ptrace_detach(struct task_struct *child, unsigned int data) { if (!valid_signal(data)) return -EIO; /* Architecture-specific hardware disable .. */ ptrace_disable(child); clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE); write_lock_irq(&tasklist_lock); /* protect against de_thread()->release_task() */ if (child->ptrace) __ptrace_detach(child, data); write_unlock_irq(&tasklist_lock); return 0; } int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len) { int copied = 0; while (len > 0) { char buf[128]; int this_len, retval; this_len = (len > sizeof(buf)) ? sizeof(buf) : len; retval = access_process_vm(tsk, src, buf, this_len, 0); if (!retval) { if (copied) break; return -EIO; } if (copy_to_user(dst, buf, retval)) return -EFAULT; copied += retval; src += retval; dst += retval; len -= retval; } return copied; } int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned long dst, int len) { int copied = 0; while (len > 0) { char buf[128]; int this_len, retval; this_len = (len > sizeof(buf)) ? sizeof(buf) : len; if (copy_from_user(buf, src, this_len)) return -EFAULT; retval = access_process_vm(tsk, dst, buf, this_len, 1); if (!retval) { if (copied) break; return -EIO; } copied += retval; src += retval; dst += retval; len -= retval; } return copied; } static int ptrace_setoptions(struct task_struct *child, long data) { child->ptrace &= ~PT_TRACE_MASK; if (data & PTRACE_O_TRACESYSGOOD) child->ptrace |= PT_TRACESYSGOOD; if (data & PTRACE_O_TRACEFORK) child->ptrace |= PT_TRACE_FORK; if (data & PTRACE_O_TRACEVFORK) child->ptrace |= PT_TRACE_VFORK; if (data & PTRACE_O_TRACECLONE) child->ptrace |= PT_TRACE_CLONE; if (data & PTRACE_O_TRACEEXEC) child->ptrace |= PT_TRACE_EXEC; if (data & PTRACE_O_TRACEVFORKDONE) child->ptrace |= PT_TRACE_VFORK_DONE; if (data & PTRACE_O_TRACEEXIT) child->ptrace |= PT_TRACE_EXIT; return (data & ~PTRACE_O_MASK) ? -EINVAL : 0; } static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info) { int error = -ESRCH; read_lock(&tasklist_lock); if (likely(child->sighand != NULL)) { error = -EINVAL; spin_lock_irq(&child->sighand->siglock); if (likely(child->last_siginfo != NULL)) { *info = *child->last_siginfo; error = 0; } spin_unlock_irq(&child->sighand->siglock); } read_unlock(&tasklist_lock); return error; } static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info) { int error = -ESRCH; read_lock(&tasklist_lock); if (likely(child->sighand != NULL)) { error = -EINVAL; spin_lock_irq(&child->sighand->siglock); if (likely(child->last_siginfo != NULL)) { *child->last_siginfo = *info; error = 0; } spin_unlock_irq(&child->sighand->siglock); } read_unlock(&tasklist_lock); return error; } #ifdef PTRACE_SINGLESTEP #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP) #else #define is_singlestep(request) 0 #endif #ifdef PTRACE_SINGLEBLOCK #define is_singleblock(request) ((request) == PTRACE_SINGLEBLOCK) #else #define is_singleblock(request) 0 #endif #ifdef PTRACE_SYSEMU #define is_sysemu_singlestep(request) ((request) == PTRACE_SYSEMU_SINGLESTEP) #else #define is_sysemu_singlestep(request) 0 #endif static int ptrace_resume(struct task_struct *child, long request, long data) { if (!valid_signal(data)) return -EIO; if (request == PTRACE_SYSCALL) set_tsk_thread_flag(child, TIF_SYSCALL_TRACE); else clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE); #ifdef TIF_SYSCALL_EMU if (request == PTRACE_SYSEMU || request == PTRACE_SYSEMU_SINGLESTEP) set_tsk_thread_flag(child, TIF_SYSCALL_EMU); else clear_tsk_thread_flag(child, TIF_SYSCALL_EMU); #endif if (is_singleblock(request)) { if (unlikely(!arch_has_block_step())) return -EIO; user_enable_block_step(child); } else if (is_singlestep(request) || is_sysemu_singlestep(request)) { if (unlikely(!arch_has_single_step())) return -EIO; user_enable_single_step(child); } else user_disable_single_step(child); child->exit_code = data; wake_up_process(child); return 0; } int ptrace_request(struct task_struct *child, long request, long addr, long data) { int ret = -EIO; siginfo_t siginfo; switch (request) { case PTRACE_PEEKTEXT: case PTRACE_PEEKDATA: return generic_ptrace_peekdata(child, addr, data); case PTRACE_POKETEXT: case PTRACE_POKEDATA: return generic_ptrace_pokedata(child, addr, data); #ifdef PTRACE_OLDSETOPTIONS case PTRACE_OLDSETOPTIONS: #endif case PTRACE_SETOPTIONS: ret = ptrace_setoptions(child, data); break; case PTRACE_GETEVENTMSG: ret = put_user(child->ptrace_message, (unsigned long __user *) data); break; case PTRACE_GETSIGINFO: ret = ptrace_getsiginfo(child, &siginfo); if (!ret) ret = copy_siginfo_to_user((siginfo_t __user *) data, &siginfo); break; case PTRACE_SETSIGINFO: if (copy_from_user(&siginfo, (siginfo_t __user *) data, sizeof siginfo)) ret = -EFAULT; else ret = ptrace_setsiginfo(child, &siginfo); break; case PTRACE_DETACH: /* detach a process that was attached. */ ret = ptrace_detach(child, data); break; #ifdef PTRACE_SINGLESTEP case PTRACE_SINGLESTEP: #endif #ifdef PTRACE_SINGLEBLOCK case PTRACE_SINGLEBLOCK: #endif #ifdef PTRACE_SYSEMU case PTRACE_SYSEMU: case PTRACE_SYSEMU_SINGLESTEP: #endif case PTRACE_SYSCALL: case PTRACE_CONT: return ptrace_resume(child, request, data); case PTRACE_KILL: if (child->exit_state) /* already dead */ return 0; return ptrace_resume(child, request, SIGKILL); default: break; } return ret; } /** * ptrace_traceme -- helper for PTRACE_TRACEME * * Performs checks and sets PT_PTRACED. * Should be used by all ptrace implementations for PTRACE_TRACEME. */ int ptrace_traceme(void) { int ret = -EPERM; /* * Are we already being traced? */ repeat: task_lock(current); if (!(current->ptrace & PT_PTRACED)) { /* * See ptrace_attach() comments about the locking here. */ unsigned long flags; if (!write_trylock_irqsave(&tasklist_lock, flags)) { task_unlock(current); do { cpu_relax(); } while (!write_can_lock(&tasklist_lock)); goto repeat; } ret = security_ptrace_traceme(current->parent); /* * Set the ptrace bit in the process ptrace flags. * Then link us on our parent's ptraced list. */ if (!ret) { current->ptrace |= PT_PTRACED; __ptrace_link(current, current->real_parent); } write_unlock_irqrestore(&tasklist_lock, flags); } task_unlock(current); return ret; } /** * ptrace_get_task_struct -- grab a task struct reference for ptrace * @pid: process id to grab a task_struct reference of * * This function is a helper for ptrace implementations. It checks * permissions and then grabs a task struct for use of the actual * ptrace implementation. * * Returns the task_struct for @pid or an ERR_PTR() on failure. */ struct task_struct *ptrace_get_task_struct(pid_t pid) { struct task_struct *child; read_lock(&tasklist_lock); child = find_task_by_vpid(pid); if (child) get_task_struct(child); read_unlock(&tasklist_lock); if (!child) return ERR_PTR(-ESRCH); return child; } #ifndef arch_ptrace_attach #define arch_ptrace_attach(child) do { } while (0) #endif asmlinkage long sys_ptrace(long request, long pid, long addr, long data) { struct task_struct *child; long ret; /* * This lock_kernel fixes a subtle race with suid exec */ lock_kernel(); if (request == PTRACE_TRACEME) { ret = ptrace_traceme(); if (!ret) arch_ptrace_attach(current); goto out; } child = ptrace_get_task_struct(pid); if (IS_ERR(child)) { ret = PTR_ERR(child); goto out; } if (request == PTRACE_ATTACH) { ret = ptrace_attach(child); /* * Some architectures need to do book-keeping after * a ptrace attach. */ if (!ret) arch_ptrace_attach(child); goto out_put_task_struct; } ret = ptrace_check_attach(child, request == PTRACE_KILL); if (ret < 0) goto out_put_task_struct; ret = arch_ptrace(child, request, addr, data); if (ret < 0) goto out_put_task_struct; out_put_task_struct: put_task_struct(child); out: unlock_kernel(); return ret; } int generic_ptrace_peekdata(struct task_struct *tsk, long addr, long data) { unsigned long tmp; int copied; copied = access_process_vm(tsk, addr, &tmp, sizeof(tmp), 0); if (copied != sizeof(tmp)) return -EIO; return put_user(tmp, (unsigned long __user *)data); } int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data) { int copied; copied = access_process_vm(tsk, addr, &data, sizeof(data), 1); return (copied == sizeof(data)) ? 0 : -EIO; } #if defined CONFIG_COMPAT && defined __ARCH_WANT_COMPAT_SYS_PTRACE #include <linux/compat.h> int compat_ptrace_request(struct task_struct *child, compat_long_t request, compat_ulong_t addr, compat_ulong_t data) { compat_ulong_t __user *datap = compat_ptr(data); compat_ulong_t word; siginfo_t siginfo; int ret; switch (request) { case PTRACE_PEEKTEXT: case PTRACE_PEEKDATA: ret = access_process_vm(child, addr, &word, sizeof(word), 0); if (ret != sizeof(word)) ret = -EIO; else ret = put_user(word, datap); break; case PTRACE_POKETEXT: case PTRACE_POKEDATA: ret = access_process_vm(child, addr, &data, sizeof(data), 1); ret = (ret != sizeof(data) ? -EIO : 0); break; case PTRACE_GETEVENTMSG: ret = put_user((compat_ulong_t) child->ptrace_message, datap); break; case PTRACE_GETSIGINFO: ret = ptrace_getsiginfo(child, &siginfo); if (!ret) ret = copy_siginfo_to_user32( (struct compat_siginfo __user *) datap, &siginfo); break; case PTRACE_SETSIGINFO: memset(&siginfo, 0, sizeof siginfo); if (copy_siginfo_from_user32( &siginfo, (struct compat_siginfo __user *) datap)) ret = -EFAULT; else ret = ptrace_setsiginfo(child, &siginfo); break; default: ret = ptrace_request(child, request, addr, data); } return ret; } asmlinkage long compat_sys_ptrace(compat_long_t request, compat_long_t pid, compat_long_t addr, compat_long_t data) { struct task_struct *child; long ret; /* * This lock_kernel fixes a subtle race with suid exec */ lock_kernel(); if (request == PTRACE_TRACEME) { ret = ptrace_traceme(); goto out; } child = ptrace_get_task_struct(pid); if (IS_ERR(child)) { ret = PTR_ERR(child); goto out; } if (request == PTRACE_ATTACH) { ret = ptrace_attach(child); /* * Some architectures need to do book-keeping after * a ptrace attach. */ if (!ret) arch_ptrace_attach(child); goto out_put_task_struct; } ret = ptrace_check_attach(child, request == PTRACE_KILL); if (!ret) ret = compat_arch_ptrace(child, request, addr, data); out_put_task_struct: put_task_struct(child); out: unlock_kernel(); return ret; } #endif /* CONFIG_COMPAT && __ARCH_WANT_COMPAT_SYS_PTRACE */