[1/1] Ban ecryptfs over ecryptfs

Submitted by Colin King on Feb. 15, 2012, 7:04 p.m.

Details

Message ID 1329332684-21429-2-git-send-email-colin.king@canonical.com
State New
Headers show

Commit Message

Colin King Feb. 15, 2012, 7:04 p.m.
From: Colin Ian King <colin.king@canonical.com>

This is a seriously simplified patch from Eric Sandeen; copy of
rationale follows:

Patch hide | download patch | download mbox

===
  mounting stacked ecryptfs on ecryptfs has been shown to lead to bugs
  in testing.  For crypto info in xattr, there is no mechanism for handling
  this at all, and for normal file headers, we run into other trouble:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
  IP: [<ffffffffa015b0b3>] ecryptfs_d_revalidate+0x43/0xa0 [ecryptfs]
  ...

  There doesn't seem to be any good usecase for this, so I'd suggest just
  disallowing the configuration.

  Based on a patch originally, I believe, from Mike Halcrow.
===

This is a backport of commit 4403158ba295c8e36f6736b1bb12d0f7e1923dac

https://bugs.launchpad.net/ubuntu/+bug/932987

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 fs/ecryptfs/main.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index f6cd392..e2f18ad 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -496,6 +496,7 @@  out:
 }
 
 struct kmem_cache *ecryptfs_sb_info_cache;
+static struct file_system_type ecryptfs_fs_type;
 
 /**
  * ecryptfs_fill_super
@@ -571,6 +572,13 @@  static int ecryptfs_read_super(struct super_block *sb, const char *dev_name,
 		ecryptfs_printk(KERN_WARNING, "path_lookup() failed\n");
 		goto out;
 	}
+	if (path.dentry->d_sb->s_type == &ecryptfs_fs_type) {
+		rc = -EINVAL;
+		printk(KERN_ERR "Mount on filesystem of type "
+			"eCryptfs explicitly disallowed due to "
+			"known incompatibilities\n");
+		goto out_free;
+	}
 
 	if (check_ruid && path.dentry->d_inode->i_uid != current_uid()) {
 		rc = -EPERM;