Data is lost if file with open descriptor is renamed before writing

[Slava0135]

Hello, we are doing research on file system testing, our fuzzer DIFFuzzer (source is closed at the moment) found this bug on commit 2cc2af5030f8bf831cd8355bc4780a34acbf6faa (tag: v2.7.10)

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

int main() {
  char buffer[100] = {0};
  int fd_0 = creat("1", S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
  rename("1", "2");
  write(fd_0, "0123456789", 10);
  close(fd_0);
  int fd_1 = open("2", O_RDWR);
  int nread = read(fd_1, buffer, 10);
  printf("%d(%s)\n", nread, strerror(errno));
  printf("%s\n", buffer);
}

// ::Expected::
// 10(Success)
// 0123456789

// ::Actual::
// 0(Success)
//

If file is renamed when there is an open file descriptor, and any data is written, it will not be saved to disk.

Instead of using read at the end you can also just cat 2 in shell.

System info:

Ubuntu 22.04.5 LTS
Kernel 5.15.178
gcc 11.4.0