Re: [PATCH] ext4: Fix WANRON caused by unconsistent boot loader inode's i_size and i_disksize

[Theodore Ts'o]

Actually, after looking more closely at swap_boot_loader_inode(), your
patch is better one.  I've dropped mine and applied yours, with commit
message clarified a bit:

    ext4: zero i_disksize when initializing the bootloader inode
    
    If the boot loader inode has never been used before, the
    EXT4_IOC_SWAP_BOOT inode will initialize it, including setting the
    i_size to 0.  However, if the "never before used" boot loader has a
    non-zero i_size, then i_disksize will be non-zero, and the
    inconsistency between i_size and i_disksize can trigger a kernel
    warning:
    
     WARNING: CPU: 0 PID: 2580 at fs/ext4/file.c:319
     CPU: 0 PID: 2580 Comm: bb Not tainted 6.3.0-rc1-00004-g703695902cfa
     RIP: 0010:ext4_file_write_iter+0xbc7/0xd10
     Call Trace:
      vfs_write+0x3b1/0x5c0
      ksys_write+0x77/0x160
      __x64_sys_write+0x22/0x30
      do_syscall_64+0x39/0x80
    
    Reproducer:
     1. create corrupted image and mount it:
           mke2fs -t ext4 /tmp/foo.img 200
           debugfs -wR "sif <5> size 25700" /tmp/foo.img
           mount -t ext4 /tmp/foo.img /mnt
           cd /mnt
           echo 123 > file
     2. Run the reproducer program:
           posix_memalign(&buf, 1024, 1024)
           fd = open("file", O_RDWR | O_DIRECT);
           ioctl(fd, EXT4_IOC_SWAP_BOOT);
           write(fd, buf, 1024);
    
    Fix this by setting i_disksize as well as i_size to zero when
    initiaizing the boot loader inode.
    
    Link: https://bugzilla.kernel.org/show_bug.cgi?id=217159
    Cc: stable@xxxxxxxxxx
    Signed-off-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230308032643.641113-1-chengzhihao1@xxxxxxxxxx
    Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>