The size of the nilfs_type_by_mode array in the fs/nilfs2/dir.c file is
defined as "S_IFMT >> S_SHIFT", but the nilfs_set_de_type() function,
which uses this array, specifies the index to read from the array in the
same way as "(mode & S_IFMT) >> S_SHIFT".

static void nilfs_set_de_type(struct nilfs_dir_entry *de, struct inode
 *inode)
{
	umode_t mode = inode->i_mode;

	de->file_type = nilfs_type_by_mode[(mode & S_IFMT)>>S_SHIFT]; // oob
}

However, when the index is determined this way, an out-of-bounds (OOB)
error occurs by referring to an index that is 1 larger than the array size
when the condition "mode & S_IFMT == S_IFMT" is satisfied.  Therefore, a
patch to resize the nilfs_type_by_mode array should be applied to prevent
OOB errors.

Link: https://lkml.kernel.org/r/20240415182048.7144-1-konishi.ryusuke@gmail.com
Reported-by: syzbot+2e22057de05b9f3b30d8@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=2e22057de05b9f3b30d8
Fixes: 2ba466d7 ("nilfs2: directory entry operations")
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>