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-rw-r--r--kernel/cred.c27
1 files changed, 26 insertions, 1 deletions
diff --git a/kernel/cred.c b/kernel/cred.c
index 8888afb846e9..e0573a43c7df 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -372,6 +372,31 @@ error_put:
return ret;
}
+static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
+{
+ const struct user_namespace *set_ns = set->user_ns;
+ const struct user_namespace *subset_ns = subset->user_ns;
+
+ /* If the two credentials are in the same user namespace see if
+ * the capabilities of subset are a subset of set.
+ */
+ if (set_ns == subset_ns)
+ return cap_issubset(subset->cap_permitted, set->cap_permitted);
+
+ /* The credentials are in a different user namespaces
+ * therefore one is a subset of the other only if a set is an
+ * ancestor of subset and set->euid is owner of subset or one
+ * of subsets ancestors.
+ */
+ for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
+ if ((set_ns == subset_ns->parent) &&
+ uid_eq(subset_ns->owner, set->euid))
+ return true;
+ }
+
+ return false;
+}
+
/**
* commit_creds - Install new credentials upon the current task
* @new: The credentials to be assigned
@@ -410,7 +435,7 @@ int commit_creds(struct cred *new)
!gid_eq(old->egid, new->egid) ||
!uid_eq(old->fsuid, new->fsuid) ||
!gid_eq(old->fsgid, new->fsgid) ||
- !cap_issubset(new->cap_permitted, old->cap_permitted)) {
+ !cred_cap_issubset(old, new)) {
if (task->mm)
set_dumpable(task->mm, suid_dumpable);
task->pdeath_signal = 0;