From 4e5adbe447db382cc76e05613581f96aef4f91d2 Mon Sep 17 00:00:00 2001
From: Tiwei Bie <tiwei.btw@antgroup.com>
Date: Thu, 24 Oct 2024 22:28:25 +0800
Subject: [PATCH] um: Add os_set_pdeathsig helper function

This helper can be used to set the parent-death signal of the calling
process to SIGKILL to ensure that the process will be killed if the
UML kernel dies unexpectedly without proper cleanup. This helper will
be used in the follow-up patches.

Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20241024142828.2612828-2-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 arch/um/include/shared/os.h | 2 ++
 arch/um/os-Linux/process.c  | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index 09f8201de5db..d709a24dc6fc 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -216,6 +216,8 @@ extern int os_drop_memory(void *addr, int length);
 extern int can_drop_memory(void);
 extern int os_mincore(void *addr, unsigned long len);
 
+void os_set_pdeathsig(void);
+
 /* execvp.c */
 extern int execvp_noalloc(char *buf, const char *file, char *const argv[]);
 /* helper.c */
diff --git a/arch/um/os-Linux/process.c b/arch/um/os-Linux/process.c
index f20602e793d9..9f086f939420 100644
--- a/arch/um/os-Linux/process.c
+++ b/arch/um/os-Linux/process.c
@@ -12,6 +12,7 @@
 #include <fcntl.h>
 #include <sys/mman.h>
 #include <sys/ptrace.h>
+#include <sys/prctl.h>
 #include <sys/wait.h>
 #include <asm/unistd.h>
 #include <init.h>
@@ -203,3 +204,8 @@ void init_new_thread_signals(void)
 	set_handler(SIGIO);
 	signal(SIGWINCH, SIG_IGN);
 }
+
+void os_set_pdeathsig(void)
+{
+	prctl(PR_SET_PDEATHSIG, SIGKILL);
+}