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Commit 116d53f0 authored by Ryusuke Konishi's avatar Ryusuke Konishi Committed by Greg Kroah-Hartman
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nilfs2: fix use-after-free bug of nilfs_root in nilfs_evict_inode() 

commit 9b5a04ac3ad9898c4745cba46ea26de74ba56a8e upstream.

During unmount process of nilfs2, nothing holds nilfs_root structure after
nilfs2 detaches its writer in nilfs_detach_log_writer().  However, since
nilfs_evict_inode() uses nilfs_root for some cleanup operations, it may
cause use-after-free read if inodes are left in "garbage_list" and
released by nilfs_dispose_list() at the end of nilfs_detach_log_writer().

Fix this issue by modifying nilfs_evict_inode() to only clear inode
without additional metadata changes that use nilfs_root if the file system
is degraded to read-only or the writer is detached.

Link: https://lkml.kernel.org/r/20230509152956.8313-1-konishi.ryusuke@gmail.com


Signed-off-by: default avatarRyusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: default avatar <syzbot+78d4495558999f55d1da@syzkaller.appspotmail.com>
Closes: https://lkml.kernel.org/r/00000000000099e5ac05fb1c3b85@google.com


Tested-by: default avatarRyusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent df89b175

fs/nilfs2/inode.c

+18 −0
Original line number Diff line number Diff line
@@ -930,6 +930,7 @@ void nilfs_evict_inode(struct inode *inode) 
	struct nilfs_transaction_info ti;

	struct super_block *sb = inode->i_sb;

	struct nilfs_inode_info *ii = NILFS_I(inode);

	struct the_nilfs *nilfs;

	int ret;



	if (inode->i_nlink || !ii->i_root || unlikely(is_bad_inode(inode))) {
@@ -942,6 +943,23 @@ void nilfs_evict_inode(struct inode *inode) 


	truncate_inode_pages_final(&inode->i_data);



	nilfs = sb->s_fs_info;

	if (unlikely(sb_rdonly(sb) || !nilfs->ns_writer)) {

		/*

		 * If this inode is about to be disposed after the file system

		 * has been degraded to read-only due to file system corruption

		 * or after the writer has been detached, do not make any

		 * changes that cause writes, just clear it.

		 * Do this check after read-locking ns_segctor_sem by

		 * nilfs_transaction_begin() in order to avoid a race with

		 * the writer detach operation.

		 */

		clear_inode(inode);

		nilfs_clear_inode(inode);

		nilfs_transaction_abort(sb);

		return;

	}



	/* TODO: some of the following operations may fail.  */

	nilfs_truncate_bmap(ii, 0);

	nilfs_mark_inode_dirty(inode);