Commit d1c2d820 authored Oct 04, 2022 by Ryusuke Konishi Committed by Greg Kroah-Hartman Oct 26, 2022

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

commit d325dc6eb763c10f591c239550b8c7e5466a5d09 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.com


Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by:  <syzbot+b8c672b0e22615c80fe0@syzkaller.appspotmail.com>
Reported-by: Khalid Masum <khalid.masum.92@gmail.com>
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent c99860f9

fs/nilfs2/inode.c

+17 −1

Original line number	Diff line number	Diff line
		@@ -340,6 +340,7 @@ 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;

		@@ -355,11 +356,26 @@ 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_msg(sb, KERN_WARNING,
		"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_msg(sb, KERN_INFO,
		"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;