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    Subject[PATCH 3.10 35/38] eCryptfs: Force RO mount when encrypted view is enabled
    Date
    3.10-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Tyler Hicks <tyhicks@canonical.com>

    commit 332b122d39c9cbff8b799007a825d94b2e7c12f2 upstream.

    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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/ecryptfs/file.c | 12 ------------
    fs/ecryptfs/main.c | 16 +++++++++++++---
    2 files changed, 13 insertions(+), 15 deletions(-)

    --- a/fs/ecryptfs/file.c
    +++ b/fs/ecryptfs/file.c
    @@ -196,23 +196,11 @@ static int ecryptfs_open(struct inode *i
    {
    int rc = 0;
    struct ecryptfs_crypt_stat *crypt_stat = NULL;
    - struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
    struct dentry *ecryptfs_dentry = file->f_path.dentry;
    /* Private value of ecryptfs_dentry allocated in
    * ecryptfs_lookup() */
    struct ecryptfs_file_info *file_info;

    - mount_crypt_stat = &ecryptfs_superblock_to_private(
    - ecryptfs_dentry->d_sb)->mount_crypt_stat;
    - if ((mount_crypt_stat->flags & ECRYPTFS_ENCRYPTED_VIEW_ENABLED)
    - && ((file->f_flags & O_WRONLY) || (file->f_flags & O_RDWR)
    - || (file->f_flags & O_CREAT) || (file->f_flags & O_TRUNC)
    - || (file->f_flags & O_APPEND))) {
    - printk(KERN_WARNING "Mount has encrypted view enabled; "
    - "files may only be read\n");
    - rc = -EPERM;
    - goto out;
    - }
    /* Released in ecryptfs_release or end of function if failure */
    file_info = kmem_cache_zalloc(ecryptfs_file_info_cache, GFP_KERNEL);
    ecryptfs_set_file_private(file, file_info);
    --- a/fs/ecryptfs/main.c
    +++ b/fs/ecryptfs/main.c
    @@ -494,6 +494,7 @@ static struct dentry *ecryptfs_mount(str
    {
    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;
    @@ -512,6 +513,7 @@ static struct dentry *ecryptfs_mount(str
    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)) {
    @@ -558,11 +560,19 @@ static struct dentry *ecryptfs_mount(str

    /**
    * 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;



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