ext4: fix use-after-iput when fscrypt contexts are inconsistent

In the case where the child's encryption context was inconsistent with
its parent directory, we were using inode->i_sb and inode->i_ino after
the inode had already been iput().  Fix this by doing the iput() in the
correct places.

Note: only ext4 had this bug, not f2fs and ubifs.

Fixes: d9cdc9033181 ("ext4 crypto: enforce context consistency")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index bb880c326191f21d276758ec00edf709edd066cb..931da9d5d9156e8f5a3c201b13f94f1ff2991b8c 100644 (file)
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1618,13 +1618,15 @@ static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, unsi
                    !fscrypt_has_permitted_context(dir, inode)) {
                        int nokey = ext4_encrypted_inode(inode) &&
                                !fscrypt_has_encryption_key(inode);
-                       iput(inode);
-                       if (nokey)
+                       if (nokey) {
+                               iput(inode);
                                return ERR_PTR(-ENOKEY);
+                       }
                        ext4_warning(inode->i_sb,
                                     "Inconsistent encryption contexts: %lu/%lu",
                                     (unsigned long) dir->i_ino,
                                     (unsigned long) inode->i_ino);
+                       iput(inode);
                        return ERR_PTR(-EPERM);
                }
        }