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nilfs2: fix use-after-free bug of nilfs_root in nilfs_evict_inode()

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commit 9b5a04ac3a 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: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: syzbot+78d4495558999f55d1da@syzkaller.appspotmail.com
Closes: https://lkml.kernel.org/r/00000000000099e5ac05fb1c3b85@google.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>
This commit is contained in:
Ryusuke Konishi 2023-05-10 00:29:56 +09:00 committed by Greg Kroah-Hartman
parent 710dee5701
commit 6b4205ea97
1 changed files with 18 additions and 0 deletions
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18
fs/nilfs2/inode.c
View file

@ -921,6 +921,7 @@ 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))) {
@ -933,6 +934,23 @@ 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);