4.18-stable review patch. If anyone has any objections, please let me know.
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From: Theodore Ts'o tytso@mit.edu
commit b50282f3241acee880514212d88b6049fb5039c8 upstream.
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@mit.edu Reported-by: Wen Xu wen.xu@gatech.edu Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/ext4/namei.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/fs/ext4/namei.c +++ b/fs/ext4/namei.c @@ -3478,6 +3478,12 @@ static int ext4_rename(struct inode *old 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)))