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ptrace: Convert ptrace_attach() to use lock guards
Created as testing for the conditional guard infrastructure.
Specifically this makes use of the following form:
scoped_cond_guard (mutex_intr, return -ERESTARTNOINTR,
&task->signal->cred_guard_mutex) {
...
}
...
return 0;
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lkml.kernel.org/r/20231102110706.568467727%40infradead.org
This commit is contained in:
Peter Zijlstra
parent
18caaedaf4
commit
5431fdd2c1
@ -226,4 +226,6 @@ static inline void task_unlock(struct task_struct *p)
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spin_unlock(&p->alloc_lock);
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}
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DEFINE_GUARD(task_lock, struct task_struct *, task_lock(_T), task_unlock(_T))
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#endif /* _LINUX_SCHED_TASK_H */
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@ -548,5 +548,31 @@ DEFINE_LOCK_GUARD_1(spinlock_irqsave, spinlock_t,
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DEFINE_LOCK_GUARD_1_COND(spinlock_irqsave, _try,
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spin_trylock_irqsave(_T->lock, _T->flags))
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DEFINE_LOCK_GUARD_1(read_lock, rwlock_t,
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read_lock(_T->lock),
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read_unlock(_T->lock))
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DEFINE_LOCK_GUARD_1(read_lock_irq, rwlock_t,
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read_lock_irq(_T->lock),
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read_unlock_irq(_T->lock))
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DEFINE_LOCK_GUARD_1(read_lock_irqsave, rwlock_t,
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read_lock_irqsave(_T->lock, _T->flags),
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read_unlock_irqrestore(_T->lock, _T->flags),
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unsigned long flags)
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DEFINE_LOCK_GUARD_1(write_lock, rwlock_t,
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write_lock(_T->lock),
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write_unlock(_T->lock))
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DEFINE_LOCK_GUARD_1(write_lock_irq, rwlock_t,
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write_lock_irq(_T->lock),
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write_unlock_irq(_T->lock))
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DEFINE_LOCK_GUARD_1(write_lock_irqsave, rwlock_t,
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write_lock_irqsave(_T->lock, _T->flags),
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write_unlock_irqrestore(_T->lock, _T->flags),
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unsigned long flags)
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#undef __LINUX_INSIDE_SPINLOCK_H
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#endif /* __LINUX_SPINLOCK_H */
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154
kernel/ptrace.c
154
kernel/ptrace.c
@ -386,71 +386,9 @@ static int check_ptrace_options(unsigned long data)
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return 0;
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}
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static int ptrace_attach(struct task_struct *task, long request,
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unsigned long addr,
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unsigned long flags)
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static inline void ptrace_set_stopped(struct task_struct *task)
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{
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bool seize = (request == PTRACE_SEIZE);
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int retval;
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retval = -EIO;
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if (seize) {
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if (addr != 0)
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goto out;
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/*
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* This duplicates the check in check_ptrace_options() because
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* ptrace_attach() and ptrace_setoptions() have historically
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* used different error codes for unknown ptrace options.
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*/
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if (flags & ~(unsigned long)PTRACE_O_MASK)
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goto out;
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retval = check_ptrace_options(flags);
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if (retval)
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return retval;
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flags = PT_PTRACED | PT_SEIZED | (flags << PT_OPT_FLAG_SHIFT);
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} else {
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flags = PT_PTRACED;
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}
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audit_ptrace(task);
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retval = -EPERM;
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if (unlikely(task->flags & PF_KTHREAD))
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goto out;
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if (same_thread_group(task, current))
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goto out;
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/*
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* Protect exec's credential calculations against our interference;
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* SUID, SGID and LSM creds get determined differently
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* under ptrace.
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*/
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retval = -ERESTARTNOINTR;
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if (mutex_lock_interruptible(&task->signal->cred_guard_mutex))
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goto out;
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task_lock(task);
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retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH_REALCREDS);
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task_unlock(task);
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if (retval)
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goto unlock_creds;
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write_lock_irq(&tasklist_lock);
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retval = -EPERM;
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if (unlikely(task->exit_state))
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goto unlock_tasklist;
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if (task->ptrace)
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goto unlock_tasklist;
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task->ptrace = flags;
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ptrace_link(task, current);
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/* SEIZE doesn't trap tracee on attach */
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if (!seize)
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send_sig_info(SIGSTOP, SEND_SIG_PRIV, task);
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spin_lock(&task->sighand->siglock);
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guard(spinlock)(&task->sighand->siglock);
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/*
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* If the task is already STOPPED, set JOBCTL_TRAP_STOP and
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@ -474,28 +412,84 @@ static int ptrace_attach(struct task_struct *task, long request,
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task->jobctl &= ~JOBCTL_STOPPED;
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signal_wake_up_state(task, __TASK_STOPPED);
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}
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}
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spin_unlock(&task->sighand->siglock);
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static int ptrace_attach(struct task_struct *task, long request,
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unsigned long addr,
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unsigned long flags)
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{
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bool seize = (request == PTRACE_SEIZE);
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int retval;
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retval = 0;
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unlock_tasklist:
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write_unlock_irq(&tasklist_lock);
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unlock_creds:
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mutex_unlock(&task->signal->cred_guard_mutex);
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out:
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if (!retval) {
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if (seize) {
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if (addr != 0)
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return -EIO;
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/*
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* We do not bother to change retval or clear JOBCTL_TRAPPING
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* if wait_on_bit() was interrupted by SIGKILL. The tracer will
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* not return to user-mode, it will exit and clear this bit in
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* __ptrace_unlink() if it wasn't already cleared by the tracee;
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* and until then nobody can ptrace this task.
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* This duplicates the check in check_ptrace_options() because
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* ptrace_attach() and ptrace_setoptions() have historically
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* used different error codes for unknown ptrace options.
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*/
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wait_on_bit(&task->jobctl, JOBCTL_TRAPPING_BIT, TASK_KILLABLE);
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proc_ptrace_connector(task, PTRACE_ATTACH);
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if (flags & ~(unsigned long)PTRACE_O_MASK)
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return -EIO;
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retval = check_ptrace_options(flags);
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if (retval)
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return retval;
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flags = PT_PTRACED | PT_SEIZED | (flags << PT_OPT_FLAG_SHIFT);
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} else {
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flags = PT_PTRACED;
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}
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return retval;
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audit_ptrace(task);
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if (unlikely(task->flags & PF_KTHREAD))
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return -EPERM;
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if (same_thread_group(task, current))
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return -EPERM;
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/*
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* Protect exec's credential calculations against our interference;
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* SUID, SGID and LSM creds get determined differently
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* under ptrace.
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*/
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scoped_cond_guard (mutex_intr, return -ERESTARTNOINTR,
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&task->signal->cred_guard_mutex) {
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scoped_guard (task_lock, task) {
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retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH_REALCREDS);
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if (retval)
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return retval;
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}
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scoped_guard (write_lock_irq, &tasklist_lock) {
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if (unlikely(task->exit_state))
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return -EPERM;
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if (task->ptrace)
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return -EPERM;
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task->ptrace = flags;
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ptrace_link(task, current);
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/* SEIZE doesn't trap tracee on attach */
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if (!seize)
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send_sig_info(SIGSTOP, SEND_SIG_PRIV, task);
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ptrace_set_stopped(task);
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}
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}
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/*
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* We do not bother to change retval or clear JOBCTL_TRAPPING
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* if wait_on_bit() was interrupted by SIGKILL. The tracer will
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* not return to user-mode, it will exit and clear this bit in
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* __ptrace_unlink() if it wasn't already cleared by the tracee;
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* and until then nobody can ptrace this task.
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*/
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wait_on_bit(&task->jobctl, JOBCTL_TRAPPING_BIT, TASK_KILLABLE);
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proc_ptrace_connector(task, PTRACE_ATTACH);
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return 0;
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}
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/**
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