[PATCH 4.9 072/153] ext4: fix use-after-iput when fscrypt contexts are inconsistent

From: Greg Kroah-Hartman
Date: Fri Mar 10 2017 - 06:18:28 EST

4.9-stable review patch. If anyone has any objections, please let me know.


From: Eric Biggers <ebiggers@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

fs/ext4/namei.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1616,13 +1616,15 @@ static struct dentry *ext4_lookup(struct
!fscrypt_has_permitted_context(dir, inode)) {
int nokey = ext4_encrypted_inode(inode) &&
- iput(inode);
- if (nokey)
+ if (nokey) {
+ iput(inode);
return ERR_PTR(-ENOKEY);
+ }
"Inconsistent encryption contexts: %lu/%lu",
(unsigned long) dir->i_ino,
(unsigned long) inode->i_ino);
+ iput(inode);
return ERR_PTR(-EPERM);