/* This demonstrates races: kernel may actually open other file then * you read at strace output. Create /tmp/delme with 10K of zeros and * 666 mode, then run this under strace. If you see open successfull * open of /etc/shadow, you know you've seen a race. */ #include #include #include #include #include #include #include int main(void) { char *c = (char*)0x94000000; int fd; open( "/tmp/delme", O_RDWR ); mmap( c, 4096, PROT_READ | PROT_WRITE, MAP_FIXED | MAP_SHARED, 3, 0 ); *c = 0; if (fork()) { while(1) { strcpy( c, "/etc/passwd" ); strcpy( c, "/etc/shadow" ); } } else while (1) if ((fd=open( c, 0 ))!=-1) close(fd); return 0; }