projects/linux·commit e6e6ec48

Merge tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt

e6e6ec48 · Linus Torvalds <[email protected]> · 2020-03-11 13:35:34 -07:00

Pull fscrypt fix from Eric Biggers:
 "Fix a bug where if userspace is writing to encrypted files while the
  FS_IOC_REMOVE_ENCRYPTION_KEY ioctl (introduced in v5.4) is running,
  dirty inodes could be evicted, causing writes could be lost or the
  filesystem to hang due to a use-after-free. This was encountered
  during real-world use, not just theoretical.

  Tested with the existing fscrypt xfstests, and with a new xfstest I
  wrote to reproduce this bug. This fix does expose an existing bug with
  '-o lazytime' that Ted is working on fixing, but this fix is more
  critical and needed anyway regardless of the lazytime fix"

* tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/fscrypt:
  fscrypt: don't evict dirty inodes after removing key
Commit
e6e6ec48dd0fa12e8a2d1ff6b55cd907401bd7fe
Parents
addcb1d0 · 2b4eae95

Merge commit. Changes below are compared with the first parent: addcb1d0.

Changes

1 files changed · +9 −0

FileStatusAddDelContent
fs/crypto/keysetup.cmodified+9−0View file

fs/crypto/keysetup.c

View file
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 65cb09f..08c9f21 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -539,6 +539,15 @@ int fscrypt_drop_inode(struct inode *inode)
mk = ci->ci_master_key->payload.data[0];
/*
+ * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes
+ * protected by the key were cleaned by sync_filesystem(). But if
+ * userspace is still using the files, inodes can be dirtied between
+ * then and now. We mustn't lose any writes, so skip dirty inodes here.
+ */
+ if (inode->i_state & I_DIRTY_ALL)
+ return 0;
+
+ /*
* Note: since we aren't holding ->mk_secret_sem, the result here can
* immediately become outdated. But there's no correctness problem with
* unnecessarily evicting. Nor is there a correctness problem with not