From 332b122d39c9cbff8b799007a825d94b2e7c12f2 Mon Sep 17 00:00:00 2001 From: Tyler Hicks Date: Tue, 7 Oct 2014 15:51:55 -0500 Subject: [PATCH] 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 Reported-by: Priya Bansal Cc: stable@vger.kernel.org # v2.6.21+: e77a56d [PATCH] eCryptfs: Encrypted passthrough --- fs/ecryptfs/file.c | 12 ------------ fs/ecryptfs/main.c | 16 +++++++++++++--- 2 files changed, 13 insertions(+), 15 deletions(-) diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c index f5bce9096555..54742f9a67a8 100644 --- a/fs/ecryptfs/file.c +++ b/fs/ecryptfs/file.c @@ -190,23 +190,11 @@ static int ecryptfs_open(struct inode *inode, struct file *file) { 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); diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c index 1b119d3bf924..34eb8433d93f 100644 --- a/fs/ecryptfs/main.c +++ b/fs/ecryptfs/main.c @@ -493,6 +493,7 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags { 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 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags 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 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags /** * 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;