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

   1 ext4: fix use-after-iput when fscrypt contexts are inconsistent
   2
   3 From: Eric Biggers <ebiggers@google.com>
   4
   5 In the case where the child's encryption context was inconsistent with
   6 its parent directory, we were using inode->i_sb and inode->i_ino after
   7 the inode had already been iput().  Fix this by doing the iput() in the
   8 correct places.
   9
  10 Note: only ext4 had this bug, not f2fs and ubifs.
  11
  12 Fixes: d9cdc9033181 ("ext4 crypto: enforce context consistency")
  13 Cc: stable@vger.kernel.org
  14 Signed-off-by: Eric Biggers <ebiggers@google.com>
  15 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  16 ---
  17  fs/ext4/namei.c | 6 ++++--
  18  1 file changed, 4 insertions(+), 2 deletions(-)
  19
  20 diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
  21 index bb880c326191..931da9d5d915 100644
  22 --- a/fs/ext4/namei.c
  23 +++ b/fs/ext4/namei.c
  24 @@ -1618,13 +1618,15 @@ static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, unsi
  25                     !fscrypt_has_permitted_context(dir, inode)) {
  26                         int nokey = ext4_encrypted_inode(inode) &&
  27                                 !fscrypt_has_encryption_key(inode);
  28 -                       iput(inode);
  29 -                       if (nokey)
  30 +                       if (nokey) {
  31 +                               iput(inode);
  32                                 return ERR_PTR(-ENOKEY);
  33 +                       }
  34                         ext4_warning(inode->i_sb,
  35                                      "Inconsistent encryption contexts: %lu/%lu",
  36                                      (unsigned long) dir->i_ino,
  37                                      (unsigned long) inode->i_ino);
  38 +                       iput(inode);
  39                         return ERR_PTR(-EPERM);
  40                 }
  41         }
  42 --
  43 2.11.0.483.g087da7b7c-goog
  44
  45