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Subject[ 13/34] Add mount option to check uid of device being mounted = expect uid, CVE-2011-1833
2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: John Johansen <john.johansen@canonical.com>

(backported from commit 764355487ea220fdc2faf128d577d7f679b91f97)

Close a TOCTOU race for mounts done via ecryptfs-mount-private. The mount
source (device) can be raced when the ownership test is done in userspace.
Provide Ecryptfs a means to force the uid check at mount time.

BugLink: http://bugs.launchpad.net/bugs/732628
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Tyler Hicks <tyler.hicks@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ecryptfs/main.c | 30 +++++++++++++++++++++++++-----
1 file changed, 25 insertions(+), 5 deletions(-)
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -212,7 +212,8 @@ enum { ecryptfs_opt_sig, ecryptfs_opt_ec
ecryptfs_opt_passthrough, ecryptfs_opt_xattr_metadata,
ecryptfs_opt_encrypted_view, ecryptfs_opt_fnek_sig,
ecryptfs_opt_fn_cipher, ecryptfs_opt_fn_cipher_key_bytes,
- ecryptfs_opt_unlink_sigs, ecryptfs_opt_err };
+ ecryptfs_opt_unlink_sigs, ecryptfs_opt_check_dev_ruid,
+ ecryptfs_opt_err };

static const match_table_t tokens = {
{ecryptfs_opt_sig, "sig=%s"},
@@ -227,6 +228,7 @@ static const match_table_t tokens = {
{ecryptfs_opt_fn_cipher, "ecryptfs_fn_cipher=%s"},
{ecryptfs_opt_fn_cipher_key_bytes, "ecryptfs_fn_key_bytes=%u"},
{ecryptfs_opt_unlink_sigs, "ecryptfs_unlink_sigs"},
+ {ecryptfs_opt_check_dev_ruid, "ecryptfs_check_dev_ruid"},
{ecryptfs_opt_err, NULL}
};

@@ -270,6 +272,7 @@ static void ecryptfs_init_mount_crypt_st
* ecryptfs_parse_options
* @sb: The ecryptfs super block
* @options: The options pased to the kernel
+ * @check_ruid: set to 1 if device uid should be checked against the ruid
*
* Parse mount options:
* debug=N - ecryptfs_verbosity level for debug output
@@ -285,7 +288,8 @@ static void ecryptfs_init_mount_crypt_st
*
* Returns zero on success; non-zero on error
*/
-static int ecryptfs_parse_options(struct super_block *sb, char *options)
+static int ecryptfs_parse_options(struct super_block *sb, char *options,
+ uid_t *check_ruid)
{
char *p;
int rc = 0;
@@ -310,6 +314,8 @@ static int ecryptfs_parse_options(struct
char *cipher_key_bytes_src;
char *fn_cipher_key_bytes_src;

+ *check_ruid = 0;
+
if (!options) {
rc = -EINVAL;
goto out;
@@ -410,6 +416,9 @@ static int ecryptfs_parse_options(struct
case ecryptfs_opt_unlink_sigs:
mount_crypt_stat->flags |= ECRYPTFS_UNLINK_SIGS;
break;
+ case ecryptfs_opt_check_dev_ruid:
+ *check_ruid = 1;
+ break;
case ecryptfs_opt_err:
default:
printk(KERN_WARNING
@@ -552,7 +561,8 @@ out:
* ecryptfs_interpose to create our initial inode and super block
* struct.
*/
-static int ecryptfs_read_super(struct super_block *sb, const char *dev_name)
+static int ecryptfs_read_super(struct super_block *sb, const char *dev_name,
+ uid_t check_ruid)
{
struct path path;
int rc;
@@ -569,6 +579,15 @@ static int ecryptfs_read_super(struct su
"known incompatibilities\n");
goto out_free;
}
+
+ if (check_ruid && path.dentry->d_inode->i_uid != current_uid()) {
+ rc = -EPERM;
+ printk(KERN_ERR "Mount of device (uid: %d) not owned by "
+ "requested user (uid: %d)\n",
+ path.dentry->d_inode->i_uid, current_uid());
+ goto out_free;
+ }
+
ecryptfs_set_superblock_lower(sb, path.dentry->d_sb);
sb->s_maxbytes = path.dentry->d_sb->s_maxbytes;
sb->s_blocksize = path.dentry->d_sb->s_blocksize;
@@ -607,6 +626,7 @@ static int ecryptfs_get_sb(struct file_s
{
int rc;
struct super_block *sb;
+ uid_t check_ruid;

rc = get_sb_nodev(fs_type, flags, raw_data, ecryptfs_fill_super, mnt);
if (rc < 0) {
@@ -614,12 +634,12 @@ static int ecryptfs_get_sb(struct file_s
goto out;
}
sb = mnt->mnt_sb;
- rc = ecryptfs_parse_options(sb, raw_data);
+ rc = ecryptfs_parse_options(sb, raw_data, &check_ruid);
if (rc) {
printk(KERN_ERR "Error parsing options; rc = [%d]\n", rc);
goto out_abort;
}
- rc = ecryptfs_read_super(sb, dev_name);
+ rc = ecryptfs_read_super(sb, dev_name, check_ruid);
if (rc) {
printk(KERN_ERR "Reading sb failed; rc = [%d]\n", rc);
goto out_abort;



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