core: use raw_clone instead of fork in signal handler

fork() is not async-signal-safe and calling it from the signal handler
could result in a deadlock when at_fork() handlers are called. Using
the raw clone() syscall sidesteps that problem.

The tricky part is that raise() does not work, since getpid() does not
work. Add raw_getpid() to get the real pid, and use kill() instead of
raise().

https://bugs.freedesktop.org/show_bug.cgi?id=86604

1 files changed, 7 insertions, 3 deletions

diff --git a/src/shared/missing.h b/src/shared/missing.h
index bea1254369..91a6215226 100644
--- a/src/shared/missing.h
+++ b/src/shared/missing.h
@@ -636,12 +636,16 @@ static inline int setns(int fd, int nstype) {
 #define CAP_AUDIT_READ 37
 #endif
 
-static inline long raw_clone(unsigned long flags, void *child_stack) {
+static inline int raw_clone(unsigned long flags, void *child_stack) {
 #if defined(__s390__) || defined(__CRIS__)
         /* On s390 and cris the order of the first and second arguments
          * of the raw clone() system call is reversed. */
-        return syscall(__NR_clone, child_stack, flags);
+        return (int) syscall(__NR_clone, child_stack, flags);
 #else
-        return syscall(__NR_clone, flags, child_stack);
+        return (int) syscall(__NR_clone, flags, child_stack);
 #endif
 }
+
+static inline pid_t raw_getpid(void) {
+        return (pid_t) syscall(__NR_getpid);
+}