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-rw-r--r--kernel/user_namespace.c37
1 files changed, 28 insertions, 9 deletions
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 8b650837083..e134d8f365d 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -21,10 +21,12 @@
#include <linux/uaccess.h>
#include <linux/ctype.h>
#include <linux/projid.h>
+#include <linux/fs_struct.h>
static struct kmem_cache *user_ns_cachep __read_mostly;
-static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid,
+static bool new_idmap_permitted(const struct file *file,
+ struct user_namespace *ns, int cap_setid,
struct uid_gid_map *map);
static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
@@ -60,6 +62,15 @@ int create_user_ns(struct cred *new)
kgid_t group = new->egid;
int ret;
+ /*
+ * Verify that we can not violate the policy of which files
+ * may be accessed that is specified by the root directory,
+ * by verifing that the root directory is at the root of the
+ * mount namespace which allows all files to be accessed.
+ */
+ if (current_chrooted())
+ return -EPERM;
+
/* The creator needs a mapping in the parent user namespace
* or else we won't be able to reasonably tell userspace who
* created a user_namespace.
@@ -86,6 +97,8 @@ int create_user_ns(struct cred *new)
set_cred_user_ns(new, ns);
+ update_mnt_policy(ns);
+
return 0;
}
@@ -600,10 +613,10 @@ static ssize_t map_write(struct file *file, const char __user *buf,
if (map->nr_extents != 0)
goto out;
- /* Require the appropriate privilege CAP_SETUID or CAP_SETGID
- * over the user namespace in order to set the id mapping.
+ /*
+ * Adjusting namespace settings requires capabilities on the target.
*/
- if (cap_valid(cap_setid) && !ns_capable(ns, cap_setid))
+ if (cap_valid(cap_setid) && !file_ns_capable(file, ns, CAP_SYS_ADMIN))
goto out;
/* Get a buffer */
@@ -688,7 +701,7 @@ static ssize_t map_write(struct file *file, const char __user *buf,
ret = -EPERM;
/* Validate the user is allowed to use user id's mapped to. */
- if (!new_idmap_permitted(ns, cap_setid, &new_map))
+ if (!new_idmap_permitted(file, ns, cap_setid, &new_map))
goto out;
/* Map the lower ids from the parent user namespace to the
@@ -775,7 +788,8 @@ ssize_t proc_projid_map_write(struct file *file, const char __user *buf, size_t
&ns->projid_map, &ns->parent->projid_map);
}
-static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid,
+static bool new_idmap_permitted(const struct file *file,
+ struct user_namespace *ns, int cap_setid,
struct uid_gid_map *new_map)
{
/* Allow mapping to your own filesystem ids */
@@ -783,12 +797,12 @@ static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid,
u32 id = new_map->extent[0].lower_first;
if (cap_setid == CAP_SETUID) {
kuid_t uid = make_kuid(ns->parent, id);
- if (uid_eq(uid, current_fsuid()))
+ if (uid_eq(uid, file->f_cred->fsuid))
return true;
}
else if (cap_setid == CAP_SETGID) {
kgid_t gid = make_kgid(ns->parent, id);
- if (gid_eq(gid, current_fsgid()))
+ if (gid_eq(gid, file->f_cred->fsgid))
return true;
}
}
@@ -799,8 +813,10 @@ static bool new_idmap_permitted(struct user_namespace *ns, int cap_setid,
/* Allow the specified ids if we have the appropriate capability
* (CAP_SETUID or CAP_SETGID) over the parent user namespace.
+ * And the opener of the id file also had the approprpiate capability.
*/
- if (ns_capable(ns->parent, cap_setid))
+ if (ns_capable(ns->parent, cap_setid) &&
+ file_ns_capable(file, ns->parent, cap_setid))
return true;
return false;
@@ -837,6 +853,9 @@ static int userns_install(struct nsproxy *nsproxy, void *ns)
if (atomic_read(&current->mm->mm_users) > 1)
return -EINVAL;
+ if (current->fs->users != 1)
+ return -EINVAL;
+
if (!ns_capable(user_ns, CAP_SYS_ADMIN))
return -EPERM;