ocfs2: validate inline xattr size and entry count in ocfs2_xattr_ibody_list

ocfs2: validate inline xattr size and entry count in ocfs2_xattr_ibody_list

Add comprehensive validation of inline xattr metadata in
ocfs2_xattr_ibody_list() to prevent out-of-bounds access and
use-after-free bugs when processing corrupted inline xattrs.

The patch adds two critical validations:

1. Validates i_xattr_inline_size before use:
   - Ensures it does not exceed block size
   - Ensures it is at least large enough for xattr header
   - Prevents pointer arithmetic with corrupted size values that could
     point outside the inode block

2. Validates xattr entry count (xh_count):
   - Calculates maximum entries that can fit in the inline space
   - Rejects counts that exceed this limit
   - Prevents out-of-bounds array access in subsequent code

Without these checks, a corrupted filesystem with invalid inline xattr
metadata can cause the code to access memory beyond the allocated space.
For example:
- A corrupted i_xattr_inline_size of 0 would cause header pointer
  calculation to point past the end of the block
- A corrupted xh_count of 22 with inline_size of 256 would cause
  array access 7 entries beyond the 15 that actually fit (the syzbot
  reproducer used xh_count of 20041), leading to use-after-free when
  accessing freed memory pages

The validation uses the correct inline_size (from di->i_xattr_inline_size)
rather than block size, ensuring accurate bounds checking for inline
xattrs specifically.

Link: https://lkml.kernel.org/r/20251120041145.33176-1-kartikey406@gmail.com
Link: https://lore.kernel.org/all/20251111073831.2027072-1-kartikey406@gmail.com/
Link: https://lore.kernel.org/all/20251117063217.5690-1-kartikey406@gmail.com/
Link: https://lore.kernel.org/all/20251117114224.12948-1-kartikey406@gmail.com/
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Reported-by: syzbot+ab0ad25088673470d2d9@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=ab0ad25088673470d2d9
Tested-by: syzbot+ab0ad25088673470d2d9@syzkaller.appspotmail.com
Suggested-by: Heming Zhao <heming.zhao@suse.com>
Reviewed-by: Heming Zhao <heming.zhao@suse.com>
Acked-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>