X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=kernel%2Fptrace.c;h=360ec5321b3b068db63216a069ceb8327f7ab3fa;hb=987b0145d94eecf292d8b301228356f44611ab7c;hp=8b2856aaf6410310d83751e1af1bef61bf447115;hpb=daddc0d38b3571bed170afa273a49a0eba090c1e;p=linux-2.6.git diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 8b2856aaf..360ec5321 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -7,6 +7,7 @@ * to continually duplicate across every architecture. */ +#include #include #include #include @@ -16,6 +17,8 @@ #include #include #include +#include +#include #include #include @@ -38,6 +41,26 @@ void __ptrace_link(task_t *child, task_t *new_parent) SET_LINKS(child); } +/* + * 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. + */ +void ptrace_untrace(task_t *child) +{ + spin_lock(&child->sighand->siglock); + if (child->state == TASK_TRACED) { + if (child->signal->flags & SIGNAL_STOP_STOPPED) { + child->state = 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. @@ -46,15 +69,18 @@ void __ptrace_link(task_t *child, task_t *new_parent) */ void __ptrace_unlink(task_t *child) { - if (!child->ptrace) - BUG(); + BUG_ON(!child->ptrace); + child->ptrace = 0; - if (list_empty(&child->ptrace_list)) - return; - list_del_init(&child->ptrace_list); - REMOVE_LINKS(child); - child->parent = child->real_parent; - SET_LINKS(child); + if (!list_empty(&child->ptrace_list)) { + list_del_init(&child->ptrace_list); + REMOVE_LINKS(child); + child->parent = child->real_parent; + SET_LINKS(child); + } + + if (child->state == TASK_TRACED) + ptrace_untrace(child); } /* @@ -62,84 +88,137 @@ void __ptrace_unlink(task_t *child) */ int ptrace_check_attach(struct task_struct *child, int kill) { - if (!(child->ptrace & PT_PTRACED)) - return -ESRCH; + int ret = -ESRCH; - if (child->parent != current) - return -ESRCH; - - if (!kill) { - if (child->state != TASK_STOPPED) - return -ESRCH; - wait_task_inactive(child); + /* + * 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 && + (!(child->ptrace & PT_ATTACHED) || child->real_parent != current) + && child->signal != NULL) { + ret = 0; + spin_lock_irq(&child->sighand->siglock); + if (child->state == TASK_STOPPED) { + child->state = TASK_TRACED; + } else if (child->state != TASK_TRACED && !kill) { + ret = -ESRCH; + } + spin_unlock_irq(&child->sighand->siglock); } + read_unlock(&tasklist_lock); /* All systems go.. */ - return 0; + return ret; +} + +static int may_attach(struct task_struct *task) +{ + if (!task->mm) + return -EPERM; + 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 && !capable(CAP_SYS_PTRACE)) + return -EPERM; + + return security_ptrace(current, task); +} + +int ptrace_may_attach(struct task_struct *task) +{ + int err; + task_lock(task); + err = may_attach(task); + task_unlock(task); + return !err; } int ptrace_attach(struct task_struct *task) { int retval; - task_lock(task); + retval = -EPERM; if (task->pid <= 1) - goto bad; - if (task == current) - goto bad; - if (!task->mm) - goto bad; - 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)) - goto bad; - rmb(); - if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE)) - goto bad; + goto out; + if (task->tgid == current->tgid) + 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); + local_irq_disable(); + if (!write_trylock(&tasklist_lock)) { + local_irq_enable(); + task_unlock(task); + do { + cpu_relax(); + } while (!write_can_lock(&tasklist_lock)); + goto repeat; + } + /* the same process cannot be attached many times */ if (task->ptrace & PT_PTRACED) goto bad; - retval = security_ptrace(current, task); + retval = may_attach(task); if (retval) goto bad; /* Go */ - task->ptrace |= PT_PTRACED; + task->ptrace |= PT_PTRACED | ((task->real_parent != current) + ? PT_ATTACHED : 0); if (capable(CAP_SYS_PTRACE)) task->ptrace |= PT_PTRACE_CAP; - task_unlock(task); - write_lock_irq(&tasklist_lock); __ptrace_link(task, current); - write_unlock_irq(&tasklist_lock); force_sig_specific(SIGSTOP, task); - return 0; bad: + write_unlock_irq(&tasklist_lock); task_unlock(task); +out: return retval; } +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 ((unsigned long) data > _NSIG) - return -EIO; + if (!valid_signal(data)) + return -EIO; /* Architecture-specific hardware disable .. */ ptrace_disable(child); - /* .. re-parent .. */ - child->exit_code = data; - write_lock_irq(&tasklist_lock); - __ptrace_unlink(child); - /* .. and wake it up. */ - if (child->state != TASK_ZOMBIE) - wake_up_process(child); + if (child->ptrace) + __ptrace_detach(child, data); write_unlock_irq(&tasklist_lock); return 0; @@ -178,8 +257,6 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, in if (bytes > PAGE_SIZE-offset) bytes = PAGE_SIZE-offset; - flush_cache_page(vma, addr); - maddr = kmap(page); if (write) { copy_to_user_page(vma, page, addr, @@ -281,18 +358,45 @@ static int ptrace_setoptions(struct task_struct *child, long data) static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data) { - if (child->last_siginfo == NULL) - return -EINVAL; - return copy_siginfo_to_user(data, child->last_siginfo); + siginfo_t lastinfo; + 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)) { + lastinfo = *child->last_siginfo; + error = 0; + } + spin_unlock_irq(&child->sighand->siglock); + } + read_unlock(&tasklist_lock); + if (!error) + return copy_siginfo_to_user(data, &lastinfo); + return error; } static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data) { - if (child->last_siginfo == NULL) - return -EINVAL; - if (copy_from_user(child->last_siginfo, data, sizeof (siginfo_t)) != 0) + siginfo_t newinfo; + int error = -ESRCH; + + if (copy_from_user(&newinfo, data, sizeof (siginfo_t))) return -EFAULT; - return 0; + + 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 = newinfo; + error = 0; + } + spin_unlock_irq(&child->sighand->siglock); + } + read_unlock(&tasklist_lock); + return error; } int ptrace_request(struct task_struct *child, long request, @@ -323,23 +427,104 @@ int ptrace_request(struct task_struct *child, long request, return ret; } -void ptrace_notify(int exit_code) +/** + * 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) { - BUG_ON (!(current->ptrace & PT_PTRACED)); - - /* Let the debugger run. */ - current->exit_code = exit_code; - set_current_state(TASK_STOPPED); - notify_parent(current, SIGCHLD); - schedule(); + int ret = -EPERM; /* - * Signals sent while we were stopped might set TIF_SIGPENDING. + * Are we already being traced? */ + task_lock(current); + if (!(current->ptrace & PT_PTRACED)) { + ret = security_ptrace(current->parent, current); + /* + * Set the ptrace bit in the process ptrace flags. + */ + if (!ret) + current->ptrace |= PT_PTRACED; + } + task_unlock(current); + return ret; +} - spin_lock_irq(¤t->sighand->siglock); - recalc_sigpending(); - spin_unlock_irq(¤t->sighand->siglock); +/** + * 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; + + /* + * Tracing init is not allowed. + */ + if (pid == 1) + return ERR_PTR(-EPERM); + + read_lock(&tasklist_lock); + child = find_task_by_pid(pid); + if (child) + get_task_struct(child); + read_unlock(&tasklist_lock); + if (!child) + return ERR_PTR(-ESRCH); + return child; } -EXPORT_SYMBOL(ptrace_notify); +#ifndef __ARCH_SYS_PTRACE +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(); + goto out; + } + + child = ptrace_get_task_struct(pid); + if (IS_ERR(child)) { + ret = PTR_ERR(child); + goto out; + } + + ret = -EPERM; + if (!vx_check(vx_task_xid(child), VX_WATCH|VX_IDENT)) + goto out_put_task_struct; + + if (request == PTRACE_ATTACH) { + ret = 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; +} +#endif /* __ARCH_SYS_PTRACE */