[PATCH 8/9] signal/task_exit: Use start_task_exit in place of do_exit

Eric W. Biederman
2021-06-24T19:03:39Z

Reuse start_task_exit_locked to implement start_task_exit.

Simplify the exit logic by having all exits go through get_signal.
This simplifies the analysis of syncrhonization during exit and
gurantees a full set of registers will be available for ptrace to
examine at PTRACE_EVENT_EXIT.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
include/linux/sched/signal.h | 1 +
kernel/exit.c | 4 +++-
kernel/seccomp.c | 2 +-
kernel/signal.c | 12 ++++++++++++
4 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index a958381ba4a9..3f4e69c019b7 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -430,6 +430,7 @@ static inline void ptrace_signal_wake_up(struct task_struct *t, bool resume)

void start_group_exit(int exit_code);
void start_task_exit_locked(struct task_struct *task, int exit_code);
+void start_task_exit(int exit_code);

void task_join_group_stop(struct task_struct *task);

diff --git a/kernel/exit.c b/kernel/exit.c
index 635f434122b7..51e0c82b3f7d 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -889,7 +889,9 @@ EXPORT_SYMBOL(complete_and_exit);

SYSCALL_DEFINE1(exit, int, error_code)
{
- do_exit((error_code&0xff)<<8);
+ start_task_exit((error_code&0xff)<<8);
+ /* get_signal will call do_exit */
+ return 0;
}

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index b1c06fd1b205..e0c4c123a8bf 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -1248,7 +1248,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
force_sig_seccomp(this_syscall, data, true);
} else {
if (action == SECCOMP_RET_KILL_THREAD)
- do_exit(SIGSYS);
+ start_task_exit(SIGSYS);
else
start_group_exit(SIGSYS);
}
diff --git a/kernel/signal.c b/kernel/signal.c
index afbc001220dd..63fda9b6bbf9 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1424,6 +1424,18 @@ void start_task_exit_locked(struct task_struct *task, int exit_code)
}
}

+void start_task_exit(int exit_code)
+{
+ struct task_struct *task = current;
+ if (!fatal_signal_pending(task)) {
+ struct sighand_struct *const sighand = task->sighand;
+ spin_lock_irq(&sighand->siglock);
+ if (!fatal_signal_pending(current))
+ start_task_exit_locked(task, exit_code);
+ spin_unlock_irq(&sighand->siglock);
+ }
+}
+
struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
unsigned long *flags)
{
--
2.20.1