Priveleged operations should be allowed on loop devices within a
devloop mount by root within the user namespace which owns the
mount. Stash away the namespace at mount time and allow
CAP_SYS_ADMIN within this namespace to perform priveleged
operations on loop devices.
Signed-off-by: Seth Forshee <seth.fors...@canonical.com>
---
drivers/block/loop.c | 27 ++++++++++++++++++++++-----
fs/loopfs/inode.c | 11 +++++++++++
include/linux/loopfs.h | 7 +++++++
3 files changed, 40 insertions(+), 5 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index b69e6e91af10..34ade8193ca1 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -86,6 +86,19 @@ static DEFINE_MUTEX(loop_index_mutex);
static int max_part;
static int part_shift;
+static bool loop_capable(struct loop_device *lo, int cap)
+{
+ struct user_namespace *ns;
+
+ if (lo->loopfs_inode) {
+ ns = loopfs_user_ns(loopfs_sb_from_inode(lo->loopfs_inode));
+ if (ns)
+ return ns_capable(ns, cap);
+ }
+
+ return capable(cap);
+}
+
/*
* Transfer functions
*/
@@ -1077,7 +1090,7 @@ loop_set_status(struct loop_device *lo, const struct
loop_info64 *info)
if (lo->lo_encrypt_key_size &&
!uid_eq(lo->lo_key_owner, uid) &&
- !capable(CAP_SYS_ADMIN))
+ !loop_capable(lo, CAP_SYS_ADMIN))
return -EPERM;
if (lo->lo_state != Lo_bound)
return -ENXIO;
@@ -1167,7 +1180,8 @@ loop_get_status(struct loop_device *lo, struct
loop_info64 *info)
memcpy(info->lo_crypt_name, lo->lo_crypt_name, LO_NAME_SIZE);
info->lo_encrypt_type =
lo->lo_encryption ? lo->lo_encryption->number : 0;
- if (lo->lo_encrypt_key_size && capable(CAP_SYS_ADMIN)) {
+ if (lo->lo_encrypt_key_size &&
+ loop_capable(lo, CAP_SYS_ADMIN)) {
info->lo_encrypt_key_size = lo->lo_encrypt_key_size;
memcpy(info->lo_encrypt_key, lo->lo_encrypt_key,
lo->lo_encrypt_key_size);
@@ -1312,7 +1326,8 @@ static int lo_ioctl(struct block_device *bdev, fmode_t
mode,
break;
case LOOP_SET_STATUS:
err = -EPERM;
- if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
+ if ((mode & FMODE_WRITE) ||
+ loop_capable(lo, CAP_SYS_ADMIN))
err = loop_set_status_old(lo,
(struct loop_info __user *)arg);
break;
@@ -1321,7 +1336,8 @@ static int lo_ioctl(struct block_device *bdev, fmode_t
mode,
break;
case LOOP_SET_STATUS64:
err = -EPERM;
- if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
+ if ((mode & FMODE_WRITE) ||
+ loop_capable(lo, CAP_SYS_ADMIN))
err = loop_set_status64(lo,
(struct loop_info64 __user *) arg);
break;
@@ -1330,7 +1346,8 @@ static int lo_ioctl(struct block_device *bdev, fmode_t
mode,
break;
case LOOP_SET_CAPACITY:
err = -EPERM;
- if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
+ if ((mode & FMODE_WRITE) ||
+ loop_capable(lo, CAP_SYS_ADMIN))
err = loop_set_capacity(lo, bdev);
break;
default:
diff --git a/fs/loopfs/inode.c b/fs/loopfs/inode.c
index 78dbaf831d9b..6410af5700c4 100644
--- a/fs/loopfs/inode.c
+++ b/fs/loopfs/inode.c
@@ -20,6 +20,7 @@
#include <linux/miscdevice.h>
#include <linux/parser.h>
#include <linux/fsnotify.h>
+#include <linux/user_namespace.h>
#include <linux/loopfs.h>
static struct vfsmount *loopfs_mnt;
@@ -31,6 +32,7 @@ struct loop_mount_opts {
struct loop_fs_info {
struct dentry *control_dentry;
struct loop_mount_opts opts;
+ struct user_namespace *user_ns;
kuid_t root_uid;
kgid_t root_gid;
};
@@ -57,6 +59,13 @@ struct super_block *loopfs_sb_from_inode(struct inode *inode)
return loopfs_mnt->mnt_sb;
}
+struct user_namespace *loopfs_user_ns(struct super_block *sb)
+{
+ if (!sb)
+ return NULL;
+ return LOOPFS_SB(sb)->user_ns;
+}
+
static int mknod_loop_control(struct super_block *sb)
{
int ret = 0;
@@ -147,6 +156,7 @@ static int loopfs_fill_super(struct super_block *s, void
*data, int silent)
return -ENOMEM;
s->s_fs_info = fsi;
+ fsi->user_ns = get_user_ns(current_user_ns());
fsi->root_uid = make_kuid(current_user_ns(), 0);
if (!uid_valid(fsi->root_uid))
@@ -237,6 +247,7 @@ cleanup:
static void loopfs_kill_sb(struct super_block *sb)
{
loop_release_devices(sb);
+ put_user_ns(LOOPFS_SB(sb)->user_ns);
kfree(LOOPFS_SB(sb));
kill_litter_super(sb);
}
diff --git a/include/linux/loopfs.h b/include/linux/loopfs.h
index 27deadd02364..a4ff5094073e 100644
--- a/include/linux/loopfs.h
+++ b/include/linux/loopfs.h
@@ -14,10 +14,12 @@
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/magic.h>
+#include <linux/user_namespace.h>
#ifdef CONFIG_BLK_DEV_LOOP
struct super_block *loopfs_sb_from_inode(struct inode *inode);
+struct user_namespace *loopfs_user_ns(struct super_block *sb);
struct inode *loopfs_new_dev(struct inode *ref_inode, dev_t device,
int lo_number);
void loopfs_kill_dev(struct inode *inode);
@@ -32,6 +34,11 @@ static inline struct super_block
*loopfs_sb_from_inode(struct inode *inode)
return NULL;
}
+static inline struct user_namespace *loopfs_user_ns(struct super_block *sb)
+{
+ return NULL;
+}
+
static inline struct inode *loopfs_new_dev(struct inode *ref_inode,
dev_t device, int lo_number)
{
--
1.9.1
--
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