linux-ext4 - [Bug 218830] New: lseek on closed file does not trigger an error and affect other files

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Date: Mon, 13 May 2024 02:39:59 +0000
From: bugzilla-daemon@...nel.org
To: linux-ext4@...r.kernel.org
Subject: [Bug 218830] New: lseek on closed file does not trigger an error and
 affect other files

https://bugzilla.kernel.org/show_bug.cgi?id=218830

            Bug ID: 218830
           Summary: lseek on closed file does not trigger an error and
                    affect other files
           Product: File System
           Version: 2.5
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P3
         Component: ext4
          Assignee: fs_ext4@...nel-bugs.osdl.org
          Reporter: zhangchi_seg@...il.nju.edu.cn
        Regression: No

Created attachment 306289
  --> https://bugzilla.kernel.org/attachment.cgi?id=306289&action=edit
reproduce.c

Hi,

I have a file and lseek on it after calling the close(), but it dose not
trigger an EBADF error. Then I open and write to another file, but the write
operation trigger an "Invalid argument" error. I can reproduce this with the
latest linux kernel https://git.kernel.org/torvalds/t/linux-6.9-rc7.tar.gz

The following is the triggering script:
```
dd if=/dev/zero of=ext4-0.img bs=1M count=120
mkfs.ext4 ext4-0.img
g++ -static reproduce.c
losetup /dev/loop0 ext4-0.img
mkdir /root/mnt
./a.out
```
After running the script, you will see an error message:
```
write failure: (Invalid argument)
```

The contents of `reproduce.c` :
```
#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <stddef.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
#include <dirent.h>

#include <string>

#include <sys/mount.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/wait.h>
#include <sys/xattr.h>
#include <sys/mount.h>
#include <sys/statfs.h>
#include <fcntl.h>

#define ALIGN 4096

void* align_alloc(size_t size) {
    void *ptr = NULL;
    int ret = posix_memalign(&ptr, ALIGN, size);
    if (ret) {
      printf("align error\n");
      exit(1);
    }
    return ptr;
}

int main()
{
    mount("/dev/loop0", "/root/mnt", "ext4", 0, "");

    creat("/root/mnt/a", S_IRWXU);
    creat("/root/mnt/b", S_IRWXU);
    int fd_a = open("/root/mnt/a", O_RDWR); 
    close(fd_a); 
    int fd_b = open("/root/mnt/b", O_RDWR | O_DIRECT); 
    int state = lseek(fd_a, 7208, SEEK_SET); 
    if (state == -1) {
      printf("lseek failure: (%s)\n", strerror(errno));
    }

    char *buf = (char*)align_alloc(4096);
    memset(buf, 'a', 4096);
    state = write(fd_b, buf, 4096);
    if (state == -1) {
      printf("write failure: (%s)\n", strerror(errno));
    }

    close(fd_b); 
    return 0;
}
```

I also found that if I remove the `O_DIRECT` flag of file b, the write
operation will not trigger an error, but the contents of b become garbled.

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