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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@kernel.org
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Link: https://lore.kernel.org/r/20230308032643.641113-1-chengzhihao1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.