ext4: check to make sure the rename(2)'s destination is not freed
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>
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index a225a21..bc727c3 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -3527,6 +3527,12 @@
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)))