[ 3.5.yuz extended stable] Patch "eCryptfs: Copy up POSIX ACL and read-only flags from lower" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    eCryptfs: Copy up POSIX ACL and read-only flags from lower

to the linux-3.5.y-queue branch of the 3.5.yuz extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to the 3.5
Linux kernel, or for any feedback related to it, please reply to
this email. For more information on extended stable, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From e6513e9a9c77188fa2def9b5f4400353cbb07739 Mon Sep 17 00:00:00 2001
From: Tyler Hicks <tyhicks at canonical.com>
Date: Mon, 11 Jun 2012 15:42:32 -0700
Subject: [PATCH] eCryptfs: Copy up POSIX ACL and read-only flags from lower
 mount

commit 069ddcda37b2cf5bb4b6031a944c0e9359213262 upstream.

When the eCryptfs mount options do not include '-o acl', but the lower
filesystem's mount options do include 'acl', the MS_POSIXACL flag is not
flipped on in the eCryptfs super block flags. This flag is what the VFS
checks in do_last() when deciding if the current umask should be applied
to a newly created inode's mode or not. When a default POSIX ACL mask is
set on a directory, the current umask is incorrectly applied to new
inodes created in the directory. This patch ignores the MS_POSIXACL flag
passed into ecryptfs_mount() and sets the flag on the eCryptfs super
block depending on the flag's presence on the lower super block.

Additionally, it is incorrect to allow a writeable eCryptfs mount on top
of a read-only lower mount. This missing check did not allow writes to
the read-only lower mount because permissions checks are still performed
on the lower filesystem's objects but it is best to simply not allow a
rw mount on top of ro mount. However, a ro eCryptfs mount on top of a rw
mount is valid and still allowed.

https://launchpad.net/bugs/1009207

Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
Reported-by: Stefan Beller <stefanbeller at googlemail.com>
Cc: John Johansen <john.johansen at canonical.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 fs/ecryptfs/main.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index 6895493..df217dc 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -505,7 +505,6 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags
 		goto out;
 	}

-	s->s_flags = flags;
 	rc = bdi_setup_and_register(&sbi->bdi, "ecryptfs", BDI_CAP_MAP_COPY);
 	if (rc)
 		goto out1;
@@ -541,6 +540,15 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags
 	}

 	ecryptfs_set_superblock_lower(s, path.dentry->d_sb);
+
+	/**
+	 * Set the POSIX ACL flag based on whether they're enabled in the lower
+	 * mount. Force a read-only eCryptfs mount if the lower mount is ro.
+	 * Allow a ro eCryptfs mount even when the lower mount is rw.
+	 */
+	s->s_flags = flags & ~MS_POSIXACL;
+	s->s_flags |= path.dentry->d_sb->s_flags & (MS_RDONLY | MS_POSIXACL);
+
 	s->s_maxbytes = path.dentry->d_sb->s_maxbytes;
 	s->s_blocksize = path.dentry->d_sb->s_blocksize;
 	s->s_magic = ECRYPTFS_SUPER_MAGIC;
--
1.7.9.5