nilfs2: fix use-after-free bug of struct nilfs_root

stable inclusion
from stable-v5.10.148
commit 21ee3cffed8fbabb669435facfd576ba18ac8652
category: bugfix
bugzilla:187877,https://gitee.com/src-openeuler/kernel/issues/I5X3MX
CVE: CVE-2022-3649

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=21ee3cffed8fbabb669435facfd576ba18ac8652

--------------------------------

commit d325dc6e upstream.

If the beginning of the inode bitmap area is corrupted on disk, an inode
with the same inode number as the root inode can be allocated and fail
soon after.  In this case, the subsequent call to nilfs_clear_inode() on
that bogus root inode will wrongly decrement the reference counter of
struct nilfs_root, and this will erroneously free struct nilfs_root,
causing kernel oopses.

This fixes the problem by changing nilfs_new_inode() to skip reserved
inode numbers while repairing the inode bitmap.

Link: https://lkml.kernel.org/r/20221003150519.39789-1-konishi.ryusuke@gmail.comSigned-off-by: NRyusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: syzbot+b8c672b0e22615c80fe0@syzkaller.appspotmail.com
Reported-by: NKhalid Masum <khalid.masum.92@gmail.com>
Tested-by: NRyusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NBaokun Li <libaokun1@huawei.com>
Reviewed-by: NZhang Yi <yi.zhang@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

fs/nilfs2/inode.c

@@ -332,6 +332,7 @@ struct inode *nilfs_new_inode(struct inode *dir, umode_t mode)
 	struct inode *inode;
 	struct nilfs_inode_info *ii;
 	struct nilfs_root *root;
+	struct buffer_head *bh;
 	int err = -ENOMEM;
 	ino_t ino;
 
@@ -347,11 +348,25 @@ struct inode *nilfs_new_inode(struct inode *dir, umode_t mode)
 	ii->i_state = BIT(NILFS_I_NEW);
 	ii->i_root = root;
 
-	err = nilfs_ifile_create_inode(root->ifile, &ino, &ii->i_bh);
+	err = nilfs_ifile_create_inode(root->ifile, &ino, &bh);
 	if (unlikely(err))
 		goto failed_ifile_create_inode;
 	/* reference count of i_bh inherits from nilfs_mdt_read_block() */
 
+	if (unlikely(ino < NILFS_USER_INO)) {
+		nilfs_warn(sb,
+			   "inode bitmap is inconsistent for reserved inodes");
+		do {
+			brelse(bh);
+			err = nilfs_ifile_create_inode(root->ifile, &ino, &bh);
+			if (unlikely(err))
+				goto failed_ifile_create_inode;
+		} while (ino < NILFS_USER_INO);
+
+		nilfs_info(sb, "repaired inode bitmap for reserved inodes");
+	}
+	ii->i_bh = bh;
+
 	atomic64_inc(&root->inodes_count);
 	inode_init_owner(inode, dir, mode);
 	inode->i_ino = ino;