[PATCH 6/9] signal: Fold do_group_exit into get_signal fixing io_uring threads

Eric W. Biederman
2021-06-24T19:02:31Z

Forld do_group_exit into get_signal as it is the last caller.

Move the group_exit logic above the PF_IO_WORKER exit, ensuring
that if an PF_IO_WORKER catches SIGKILL every thread in
the thread group will exit not just the the PF_IO_WORKER.

Now that the information is easily available only set PF_SIGNALED
when it was a signal that caused the exit.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
include/linux/sched/task.h | 1 -
kernel/exit.c | 31 -------------------------------
kernel/signal.c | 35 +++++++++++++++++++++++++----------
3 files changed, 25 insertions(+), 42 deletions(-)

diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index ef02be869cf2..45525512e3d0 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -77,7 +77,6 @@ static inline void exit_thread(struct task_struct *tsk)
{
}
#endif
-extern void do_group_exit(int);

extern void exit_files(struct task_struct *);
extern void exit_itimers(struct signal_struct *);
diff --git a/kernel/exit.c b/kernel/exit.c
index 921519d80b56..635f434122b7 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -892,37 +892,6 @@ SYSCALL_DEFINE1(exit, int, error_code)
do_exit((error_code&0xff)<<8);
}

-/*
- * Take down every thread in the group. This is called by fatal signals
- * as well as by sys_exit_group (below).
- */
-void
-do_group_exit(int exit_code)
-{
- struct signal_struct *sig = current->signal;
-
- BUG_ON(exit_code & 0x80); /* core dumps don't get here */
-
- if (signal_group_exit(sig))
- exit_code = sig->group_exit_code;
- else if (!thread_group_empty(current)) {
- struct sighand_struct *const sighand = current->sighand;
-
- spin_lock_irq(&sighand->siglock);
- if (signal_group_exit(sig))
- /* Another thread got here before we took the lock. */
- exit_code = sig->group_exit_code;
- else {
- sig->group_exit_code = exit_code;
- sig->flags = SIGNAL_GROUP_EXIT;
- zap_other_threads(current);
- }
- spin_unlock_irq(&sighand->siglock);
- }
-
- do_exit(exit_code);
- /* NOTREACHED */
-}

/*
* this kills every thread in the thread group. Note that any externally
diff --git a/kernel/signal.c b/kernel/signal.c
index c79c010ca5f3..95a076af600a 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2646,6 +2646,7 @@ bool get_signal(struct ksignal *ksig)
{
struct sighand_struct *sighand = current->sighand;
struct signal_struct *signal = current->signal;
+ int exit_code;
int signr;

if (unlikely(current->task_works))
@@ -2848,8 +2849,6 @@ bool get_signal(struct ksignal *ksig)
/*
* Anything else is fatal, maybe with a core dump.
*/
- current->flags |= PF_SIGNALED;
-
if (sig_kernel_coredump(signr)) {
if (print_fatal_signals)
print_fatal_signal(ksig->info.si_signo);
@@ -2857,14 +2856,33 @@ bool get_signal(struct ksignal *ksig)
/*
* If it was able to dump core, this kills all
* other threads in the group and synchronizes with
- * their demise. If we lost the race with another
- * thread getting here, it set group_exit_code
- * first and our do_group_exit call below will use
- * that value and ignore the one we pass it.
+ * their demise. If another thread makes it
+ * to do_coredump first, it will set group_exit_code
+ * which will be passed to do_exit.
*/
do_coredump(&ksig->info);
}

+ /*
+ * Death signals, no core dump.
+ */
+ exit_code = signr;
+ if (signal_group_exit(signal)) {
+ exit_code = signal->group_exit_code;
+ } else {
+ spin_lock_irq(&sighand->siglock);
+ if (signal_group_exit(signal)) {
+ /* Another thread got here before we took the lock. */
+ exit_code = signal->group_exit_code;
+ } else {
+ start_group_exit_locked(signal, exit_code);
+ }
+ spin_unlock_irq(&sighand->siglock);
+ }
+
+ if (exit_code & 0x7f)
+ current->flags |= PF_SIGNALED;
+
/*
* PF_IO_WORKER threads will catch and exit on fatal signals
* themselves. They have cleanup that must be performed, so
@@ -2873,10 +2891,7 @@ bool get_signal(struct ksignal *ksig)
if (current->flags & PF_IO_WORKER)
goto out;

- /*
- * Death signals, no core dump.
- */
- do_group_exit(ksig->info.si_signo);
+ do_exit(exit_code);
/* NOTREACHED */
}
spin_unlock_irq(&sighand->siglock);
--
2.20.1