ocfs2: add suballoc slot check in ocfs2_validate_inode_block()

In 'ocfs2_validate_inode_block()', add suballoc slot check similar to one
in 'ocfs2_get_suballoc_slot_bit()', thus preventing an out-of-bounds
accesses for 'local_system_inodes' in 'get_local_system_inode()'.

Most likely this fixes
https://syzkaller.appspot.com/bug?extid=a77d690840e60bc2ddd8 as well.

Link: https://lkml.kernel.org/r/20250826095106.666980-1-dmantipov@yandex.ru
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Reported-by: syzbot+900962ac9bf1860033f2@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=900962ac9bf1860033f2
Reviewed-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>

Author: dmantipov

fs/ocfs2/inode.c

@@ -1495,6 +1495,14 @@ int ocfs2_validate_inode_block(struct super_block *sb,
 		goto bail;
 	}
 
+	if (le16_to_cpu(di->i_suballoc_slot) != (u16)OCFS2_INVALID_SLOT &&
+	    (u32)le16_to_cpu(di->i_suballoc_slot) > OCFS2_SB(sb)->max_slots - 1) {
+		rc = ocfs2_error(sb, "Invalid dinode %llu: suballoc slot %u\n",
+				 (unsigned long long)bh->b_blocknr,
+				 le16_to_cpu(di->i_suballoc_slot));
+		goto bail;
+	}
+
 	rc = 0;
 
 bail: