From 9f9bcf679e6f627d7bd8b6e21c80906946db65b7 Mon Sep 17 00:00:00 2001
From: Thomas Voss <mail@thomasvoss.com>
Date: Thu, 21 Dec 2023 18:34:26 +0100
Subject: Add mmap-race

---
 c/mmap-race/.gitignore |  1 +
 c/mmap-race/Makefile   |  8 ++++++
 c/mmap-race/foo        |  1 +
 c/mmap-race/main.c     | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 77 insertions(+)
 create mode 100644 c/mmap-race/.gitignore
 create mode 100644 c/mmap-race/Makefile
 create mode 100644 c/mmap-race/foo
 create mode 100644 c/mmap-race/main.c

diff --git a/c/mmap-race/.gitignore b/c/mmap-race/.gitignore
new file mode 100644
index 0000000..2b7e469
--- /dev/null
+++ b/c/mmap-race/.gitignore
@@ -0,0 +1 @@
+mmap-race
diff --git a/c/mmap-race/Makefile b/c/mmap-race/Makefile
new file mode 100644
index 0000000..364bf5e
--- /dev/null
+++ b/c/mmap-race/Makefile
@@ -0,0 +1,8 @@
+include ../base.mk
+
+all: mmap-race
+mmap-race: main.c
+	$(CC) $(CFLAGS) -o $@ $<
+
+clean:
+	rm -f mmap-race
diff --git a/c/mmap-race/foo b/c/mmap-race/foo
new file mode 100644
index 0000000..4b5fa63
--- /dev/null
+++ b/c/mmap-race/foo
@@ -0,0 +1 @@
+hello, world
diff --git a/c/mmap-race/main.c b/c/mmap-race/main.c
new file mode 100644
index 0000000..d809688
--- /dev/null
+++ b/c/mmap-race/main.c
@@ -0,0 +1,67 @@
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+
+#include <err.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#define die(...) err(EXIT_FAILURE, __VA_ARGS__)
+
+static void chld(void);
+static void prnt(void);
+
+int
+main(void)
+{
+	pid_t pid;
+	switch (pid = fork()) {
+	case -1:
+		die("fork");
+	case 0:
+		chld();
+		break;
+	default:
+		prnt();
+	}
+	return EXIT_SUCCESS;
+}
+
+void
+chld(void)
+{
+	int fd;
+
+	sleep(1);
+	if ((fd = open("foo", O_WRONLY)) == -1)
+		die("open: foo");
+	if (write(fd, "overwritten", sizeof("overwritten") - 1) == -1)
+		die("write");
+
+	close(fd);
+}
+
+void
+prnt(void)
+{
+	int fd;
+	char *buf;
+	struct stat sb;
+
+	if ((fd = open("foo", O_RDONLY)) == -1)
+		die("open: foo");
+	if (fstat(fd, &sb) == -1)
+		die("fstat: foo");
+	if ((buf = mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0))
+	    == MAP_FAILED)
+		die("mmap");
+
+	wait(NULL);
+	write(STDOUT_FILENO, buf, sb.st_size);
+
+	munmap(buf, sb.st_size);
+	close(fd);
+}
-- 
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