Commit 8742f229 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds

userns: limit the maximum depth of user_namespace->parent chain

Ensure that user_namespace->parent chain can't grow too much.
Currently we use the hardroded 32 as limit.
Reported-by: default avatarAndy Lutomirski <luto@amacapital.net>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 55f5bfd4
...@@ -23,6 +23,7 @@ struct user_namespace { ...@@ -23,6 +23,7 @@ struct user_namespace {
struct uid_gid_map projid_map; struct uid_gid_map projid_map;
atomic_t count; atomic_t count;
struct user_namespace *parent; struct user_namespace *parent;
int level;
kuid_t owner; kuid_t owner;
kgid_t group; kgid_t group;
unsigned int proc_inum; unsigned int proc_inum;
......
...@@ -62,6 +62,9 @@ int create_user_ns(struct cred *new) ...@@ -62,6 +62,9 @@ int create_user_ns(struct cred *new)
kgid_t group = new->egid; kgid_t group = new->egid;
int ret; int ret;
if (parent_ns->level > 32)
return -EUSERS;
/* /*
* Verify that we can not violate the policy of which files * Verify that we can not violate the policy of which files
* may be accessed that is specified by the root directory, * may be accessed that is specified by the root directory,
...@@ -92,6 +95,7 @@ int create_user_ns(struct cred *new) ...@@ -92,6 +95,7 @@ int create_user_ns(struct cred *new)
atomic_set(&ns->count, 1); atomic_set(&ns->count, 1);
/* Leave the new->user_ns reference with the new user namespace. */ /* Leave the new->user_ns reference with the new user namespace. */
ns->parent = parent_ns; ns->parent = parent_ns;
ns->level = parent_ns->level + 1;
ns->owner = owner; ns->owner = owner;
ns->group = group; ns->group = group;
......
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