From f2f0b00ad61d53adfecb8bdf8f3cf8f05f6ed548 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 17 Jun 2009 16:27:32 -0700 Subject: [PATCH] ptrace: cleanup check/set of PT_PTRACED during attach ptrace_attach() and ptrace_traceme() are the last functions which look as if the untraced task can have task->ptrace != 0, this must not be possible. Change the code to just check ->ptrace != 0 and s/|=/=/ to set PT_PTRACED. Also, a couple of trivial whitespace cleanups in ptrace_attach(). And move ptrace_traceme() up near ptrace_attach() to keep them close to each other. Signed-off-by: Oleg Nesterov Cc: Chris Wright Acked-by: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/ptrace.c | 101 ++++++++++++++++++++++++------------------------ 1 file changed, 51 insertions(+), 50 deletions(-) diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 9439bd3331a6..12e21a949db1 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -177,12 +177,13 @@ int ptrace_attach(struct task_struct *task) if (same_thread_group(task, current)) goto out; - /* Protect the target's credential calculations against our + /* + * Protect exec's credential calculations against our interference; * interference; SUID, SGID and LSM creds get determined differently * under ptrace. */ retval = mutex_lock_interruptible(&task->cred_guard_mutex); - if (retval < 0) + if (retval < 0) goto out; repeat: /* @@ -210,10 +211,10 @@ repeat: retval = -EPERM; if (unlikely(task->exit_state)) goto bad; - if (task->ptrace & PT_PTRACED) + if (task->ptrace) goto bad; - task->ptrace |= PT_PTRACED; + task->ptrace = PT_PTRACED; if (capable(CAP_SYS_PTRACE)) task->ptrace |= PT_PTRACE_CAP; @@ -229,6 +230,52 @@ out: return retval; } +/** + * 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) { + /* + * 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); + + /* + * Check PF_EXITING to ensure ->real_parent has not passed + * exit_ptrace(). Otherwise we don't report the error but + * pretend ->real_parent untraces us right after return. + */ + if (!ret && !(current->real_parent->flags & PF_EXITING)) { + current->ptrace = PT_PTRACED; + __ptrace_link(current, current->real_parent); + } + + write_unlock_irqrestore(&tasklist_lock, flags); + } + task_unlock(current); + return ret; +} + /* * Called with irqs disabled, returns true if childs should reap themselves. */ @@ -567,52 +614,6 @@ int ptrace_request(struct task_struct *child, long request, 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); - - /* - * Check PF_EXITING to ensure ->real_parent has not passed - * exit_ptrace(). Otherwise we don't report the error but - * pretend ->real_parent untraces us right after return. - */ - if (!ret && !(current->real_parent->flags & PF_EXITING)) { - 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 -- 2.20.1