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

commit dd01b690f8f4b1e414f89e5a9a5326bf720d6652 upstream.

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")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 104f8bfba718..c4a389a6027b 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1616,13 +1616,15 @@ 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);
                 }
         }