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authorEric W. Biederman <ebiederm@xmission.com>2012-07-26 05:05:21 -0700
committerEric W. Biederman <ebiederm@xmission.com>2012-11-20 04:17:44 -0800
commit4c44aaafa8108f584831850ab48a975e971db2de (patch)
treec86f225e8256d28271acf3ea8926e70358f3e5c1 /security
parentbcf58e725ddc45d31addbc6627d4f0edccc824c1 (diff)
downloadlinux-4c44aaafa8108f584831850ab48a975e971db2de.tar.gz
userns: Kill task_user_ns
The task_user_ns function hides the fact that it is getting the user namespace from struct cred on the task. struct cred may go away as soon as the rcu lock is released. This leads to a race where we can dereference a stale user namespace pointer. To make it obvious a struct cred is involved kill task_user_ns. To kill the race modify the users of task_user_ns to only reference the user namespace while the rcu lock is held. Cc: Kees Cook <keescook@chromium.org> Cc: James Morris <james.l.morris@oracle.com> Acked-by: Kees Cook <keescook@chromium.org> Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'security')
-rw-r--r--security/yama/yama_lsm.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index b4c29848b49..0e72239aeb0 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -262,14 +262,18 @@ int yama_ptrace_access_check(struct task_struct *child,
/* No additional restrictions. */
break;
case YAMA_SCOPE_RELATIONAL:
+ rcu_read_lock();
if (!task_is_descendant(current, child) &&
!ptracer_exception_found(current, child) &&
- !ns_capable(task_user_ns(child), CAP_SYS_PTRACE))
+ !ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
rc = -EPERM;
+ rcu_read_unlock();
break;
case YAMA_SCOPE_CAPABILITY:
- if (!ns_capable(task_user_ns(child), CAP_SYS_PTRACE))
+ rcu_read_lock();
+ if (!ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
rc = -EPERM;
+ rcu_read_unlock();
break;
case YAMA_SCOPE_NO_ATTACH:
default:
@@ -307,8 +311,10 @@ int yama_ptrace_traceme(struct task_struct *parent)
/* Only disallow PTRACE_TRACEME on more aggressive settings. */
switch (ptrace_scope) {
case YAMA_SCOPE_CAPABILITY:
- if (!ns_capable(task_user_ns(parent), CAP_SYS_PTRACE))
+ rcu_read_lock();
+ if (!ns_capable(__task_cred(parent)->user_ns, CAP_SYS_PTRACE))
rc = -EPERM;
+ rcu_read_unlock();
break;
case YAMA_SCOPE_NO_ATTACH:
rc = -EPERM;