1 #include <stdio.h> 2 #include <unistd.h> 3 #include <fcntl.h> 4 #include <linux/sched.h> 5 #include <stdlib.h> 6 7 int v, fd; 8 9 int child_proc() 10 { 11 v = 42; 12 close(fd); 13 exit(0); 14 } 15 16 #define STACK_SIZE 1024 17 18 int main(int argc, char *argv[]) 19 { 20 void **child_stack; 21 char ch; 22 23 v = 9; 24 fd = open(argv[0], O_RDONLY); 25 if (read(fd, &ch, 1) < 1) { 26 printf("Can't read file"); 27 exit(1); 28 } 29 child_stack = (void **) malloc(STACK_SIZE * sizeof(void *)); 30 printf("v = %d\n", v); 31 32 clone(child_proc, child_stack + STACK_SIZE, CLONE_VM|CLONE_FILES, NULL); 33 sleep(1); 34 35 printf("v = %d\n", v); 36 if (read(fd, &ch, 1) < 1) { 37 printf("Can't read file because it's closed by child.\n"); 38 return 0; 39 } else { 40 printf("We shouldn't be able to read from file which is closed by child.\n"); 41 return 0; 42 } 43 } 44 45
