eCryptfs: Force RO mount when encrypted view is enabled
The ecryptfs_encrypted_view mount option greatly changes the
functionality of an eCryptfs mount. Instead of encrypting and decrypting
lower files, it provides a unified view of the encrypted files in the
lower filesystem. The presence of the ecryptfs_encrypted_view mount
option is intended to force a read-only mount and modifying files is not
supported when the feature is in use. See the following commit for more
information:
e77a56d [PATCH] eCryptfs: Encrypted passthrough
This patch forces the mount to be read-only when the
ecryptfs_encrypted_view mount option is specified by setting the
MS_RDONLY flag on the superblock. Additionally, this patch removes some
broken logic in ecryptfs_open() that attempted to prevent modifications
of files when the encrypted view feature was in use. The check in
ecryptfs_open() was not sufficient to prevent file modifications using
system calls that do not operate on a file descriptor.
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Reported-by: Priya Bansal <p.bansal@samsung.com>
Cc: stable@vger.kernel.org # v2.6.21+: e77a56d [PATCH] eCryptfs: Encrypted passthrough
diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index 1b119d3..34eb843 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -493,6 +493,7 @@
{
struct super_block *s;
struct ecryptfs_sb_info *sbi;
+ struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
struct ecryptfs_dentry_info *root_info;
const char *err = "Getting sb failed";
struct inode *inode;
@@ -511,6 +512,7 @@
err = "Error parsing options";
goto out;
}
+ mount_crypt_stat = &sbi->mount_crypt_stat;
s = sget(fs_type, NULL, set_anon_super, flags, NULL);
if (IS_ERR(s)) {
@@ -557,11 +559,19 @@
/**
* 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.
+ * mount.
*/
s->s_flags = flags & ~MS_POSIXACL;
- s->s_flags |= path.dentry->d_sb->s_flags & (MS_RDONLY | MS_POSIXACL);
+ s->s_flags |= path.dentry->d_sb->s_flags & MS_POSIXACL;
+
+ /**
+ * Force a read-only eCryptfs mount when:
+ * 1) The lower mount is ro
+ * 2) The ecryptfs_encrypted_view mount option is specified
+ */
+ if (path.dentry->d_sb->s_flags & MS_RDONLY ||
+ mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
+ s->s_flags |= MS_RDONLY;
s->s_maxbytes = path.dentry->d_sb->s_maxbytes;
s->s_blocksize = path.dentry->d_sb->s_blocksize;