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signal: Remove the bogus sigkill_pending in ptrace_stop
commit7d613f9f72
upstream. The existence of sigkill_pending is a little silly as it is functionally a duplicate of fatal_signal_pending that is used in exactly one place. Checking for pending fatal signals and returning early in ptrace_stop is actively harmful. It casues the ptrace_stop called by ptrace_signal to return early before setting current->exit_code. Later when ptrace_signal reads the signal number from current->exit_code is undefined, making it unpredictable what will happen. Instead rely on the fact that schedule will not sleep if there is a pending signal that can awaken a task. Removing the explict sigkill_pending test fixes fixes ptrace_signal when ptrace_stop does not stop because current->exit_code is always set to to signr. Cc: stable@vger.kernel.org Fixes:3d749b9e67
("ptrace: simplify ptrace_stop()->sigkill_pending() path") Fixes:1a669c2f16
("Add arch_ptrace_stop") Link: https://lkml.kernel.org/r/87pmsyx29t.fsf@disp2133 Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 4 additions and 14 deletions
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@ -2101,15 +2101,6 @@ static inline bool may_ptrace_stop(void)
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return true;
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}
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/*
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* Return non-zero if there is a SIGKILL that should be waking us up.
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* Called with the siglock held.
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*/
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static bool sigkill_pending(struct task_struct *tsk)
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{
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return sigismember(&tsk->pending.signal, SIGKILL) ||
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sigismember(&tsk->signal->shared_pending.signal, SIGKILL);
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}
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/*
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* This must be called with current->sighand->siglock held.
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@ -2136,17 +2127,16 @@ static void ptrace_stop(int exit_code, int why, int clear_code, kernel_siginfo_t
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* calling arch_ptrace_stop, so we must release it now.
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* To preserve proper semantics, we must do this before
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* any signal bookkeeping like checking group_stop_count.
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* Meanwhile, a SIGKILL could come in before we retake the
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* siglock. That must prevent us from sleeping in TASK_TRACED.
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* So after regaining the lock, we must check for SIGKILL.
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*/
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spin_unlock_irq(¤t->sighand->siglock);
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arch_ptrace_stop(exit_code, info);
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spin_lock_irq(¤t->sighand->siglock);
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if (sigkill_pending(current))
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return;
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}
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/*
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* schedule() will not sleep if there is a pending signal that
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* can awaken the task.
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*/
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set_special_state(TASK_TRACED);
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/*
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