[PATCH stable 6.12 1/9] um: Add os_set_pdeathsig helper function

[Florian Fainelli <florian.fainelli@broadcom.com>]

From: Tiwei Bie <tiwei.btw@antgroup.com>

commit 4e5adbe447db382cc76e05613581f96aef4f91d2 upstream

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>
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.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 77a8593f219a..2a0843cc2208 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -219,6 +219,8 @@ extern int os_unmap_memory(void *addr, int len);
 extern int os_drop_memory(void *addr, int length);
 extern int can_drop_memory(void);
 
+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 2686120ab232..4015d3dc3958 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>
@@ -234,3 +235,8 @@ void init_new_thread_signals(void)
 	set_handler(SIGIO);
 	signal(SIGWINCH, SIG_IGN);
 }
+
+void os_set_pdeathsig(void)
+{
+	prctl(PR_SET_PDEATHSIG, SIGKILL);
+}
-- 
2.34.1