If the destination of the rename(2) system call exists, the inode's link count (i_nlinks) must be non-zero. If it is, the inode can end up on the orphan list prematurely, leading to all sorts of hilarity, including a use-after-free. https://bugzilla.kernel.org/show_bug.cgi?id=200931 Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Reported-by: Wen Xu <wen.xu@xxxxxxxxxx> --- fs/ext4/namei.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c index 116ff68c5bd4..377d516c475f 100644 --- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -3478,6 +3478,12 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry, int credits; u8 old_file_type; + if (new.inode && new.inode->i_nlink == 0) { + EXT4_ERROR_INODE(new.inode, + "target of rename is already freed"); + return -EFSCORRUPTED; + } + if ((ext4_test_inode_flag(new_dir, EXT4_INODE_PROJINHERIT)) && (!projid_eq(EXT4_I(new_dir)->i_projid, EXT4_I(old_dentry->d_inode)->i_projid))) -- 2.18.0.rc0
