linux-kernel - [PATCH 12/17] signal: Compute the process exit_code in get

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Date:   Mon,  3 Jan 2022 15:33:07 -0600
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arch@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Al Viro <viro@...IV.linux.org.uk>,
        Kees Cook <keescook@...omium.org>, linux-api@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 12/17] signal: Compute the process exit_code in get_signal

In prepartion for moving the work of sys_exit and sys_group_exit into
get_signal compute exit_code in get_signal, make PF_SIGNALED depend on
the exit_code and pass the exit_code to do_group_exit.

Anytime there is a group exit the exit_code may differ from the signal
number.

To match the historical precedent as best I can make the exit_code 0
during exec. (The exit_code field would not have been set but probably
would have been left at a value of 0).

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 kernel/signal.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index fd3c404de8b6..2a24cca00ca1 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2707,6 +2707,7 @@ bool get_signal(struct ksignal *ksig)
 	for (;;) {
 		struct k_sigaction *ka;
 		enum pid_type type;
+		int exit_code;
 
 		/* Has this task already been marked for death? */
 		if ((signal->flags & SIGNAL_GROUP_EXIT) ||
@@ -2716,6 +2717,10 @@ bool get_signal(struct ksignal *ksig)
 			trace_signal_deliver(SIGKILL, SEND_SIG_NOINFO,
 				&sighand->action[SIGKILL - 1]);
 			recalc_sigpending();
+			if (signal->flags & SIGNAL_GROUP_EXIT)
+				exit_code = signal->group_exit_code;
+			else
+				exit_code = 0;
 			goto fatal;
 		}
 
@@ -2837,15 +2842,17 @@ bool get_signal(struct ksignal *ksig)
 			continue;
 		}
 
+		/*
+		 * Anything else is fatal, maybe with a core dump.
+		 */
+		exit_code = signr;
 	fatal:
 		spin_unlock_irq(&sighand->siglock);
 		if (unlikely(cgroup_task_frozen(current)))
 			cgroup_leave_frozen(true);
 
-		/*
-		 * Anything else is fatal, maybe with a core dump.
-		 */
-		current->flags |= PF_SIGNALED;
+		if (exit_code & 0x7f)
+			current->flags |= PF_SIGNALED;
 
 		if (sig_kernel_coredump(signr)) {
 			if (print_fatal_signals)
@@ -2873,7 +2880,7 @@ bool get_signal(struct ksignal *ksig)
 		/*
 		 * Death signals, no core dump.
 		 */
-		do_group_exit(ksig->info.si_signo);
+		do_group_exit(exit_code);
 		/* NOTREACHED */
 	}
 	spin_unlock_irq(&sighand->siglock);
-- 
2.29.2