From 3f8f7b4ef6d97ba0015e675fd46c329869712e7e Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Wed, 1 Sep 2021 13:21:34 -0500 Subject: signal: Remove the bogus sigkill_pending in ptrace_stop commit 7d613f9f72ec8f90ddefcae038fdae5adb8404b3 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: 3d749b9e676b ("ptrace: simplify ptrace_stop()->sigkill_pending() path") Fixes: 1a669c2f16d4 ("Add arch_ptrace_stop") Link: https://lkml.kernel.org/r/87pmsyx29t.fsf@disp2133 Reviewed-by: Kees Cook Signed-off-by: "Eric W. Biederman" Signed-off-by: Greg Kroah-Hartman --- kernel/signal.c | 17 ++--------------- 1 file changed, 2 insertions(+), 15 deletions(-) (limited to 'kernel') diff --git a/kernel/signal.c b/kernel/signal.c index 6aa9ca45ebb1..a699055ebfe8 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1823,16 +1823,6 @@ static inline int may_ptrace_stop(void) return 1; } -/* - * Return non-zero if there is a SIGKILL that should be waking us up. - * Called with the siglock held. - */ -static int sigkill_pending(struct task_struct *tsk) -{ - return sigismember(&tsk->pending.signal, SIGKILL) || - sigismember(&tsk->signal->shared_pending.signal, SIGKILL); -} - /* * This must be called with current->sighand->siglock held. * @@ -1858,15 +1848,10 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info) * calling arch_ptrace_stop, so we must release it now. * To preserve proper semantics, we must do this before * any signal bookkeeping like checking group_stop_count. - * Meanwhile, a SIGKILL could come in before we retake the - * siglock. That must prevent us from sleeping in TASK_TRACED. - * So after regaining the lock, we must check for SIGKILL. */ spin_unlock_irq(¤t->sighand->siglock); arch_ptrace_stop(exit_code, info); spin_lock_irq(¤t->sighand->siglock); - if (sigkill_pending(current)) - return; } /* @@ -1875,6 +1860,8 @@ static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info) * Also, transition to TRACED and updates to ->jobctl should be * atomic with respect to siglock and should be done after the arch * hook as siglock is released and regrabbed across it. + * schedule() will not sleep if there is a pending signal that + * can awaken the task. */ set_current_state(TASK_TRACED); -- cgit v1.2.3