4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tyler Hicks <tyhicks@xxxxxxxxxxxxx>
commit 98f368e9e2630a3ce3e80fb10fb2e02038cf9578 upstream.
When checking the current cred for a capability in a specific user
namespace, it isn't always desirable to have the LSMs audit the check.
This patch adds a noaudit variant of ns_capable() for when those
situations arise.
The common logic between ns_capable() and the new ns_capable_noaudit()
is moved into a single, shared function to keep duplicated code to a
minimum and ease maintainability.
Signed-off-by: Tyler Hicks <tyhicks@xxxxxxxxxxxxx>
Acked-by: Serge E. Hallyn <serge.hallyn@xxxxxxxxxx>
Signed-off-by: James Morris <james.l.morris@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/capability.h | 5 ++++
kernel/capability.c | 46 +++++++++++++++++++++++++++++++++++----------
2 files changed, 41 insertions(+), 10 deletions(-)
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -214,6 +214,7 @@ extern bool has_ns_capability_noaudit(st
struct user_namespace *ns, int cap);
extern bool capable(int cap);
extern bool ns_capable(struct user_namespace *ns, int cap);
+extern bool ns_capable_noaudit(struct user_namespace *ns, int cap);
#else
static inline bool has_capability(struct task_struct *t, int cap)
{
@@ -241,6 +242,10 @@ static inline bool ns_capable(struct use
{
return true;
}
+static inline bool ns_capable_noaudit(struct user_namespace *ns, int cap)
+{
+ return true;
+}
#endif /* CONFIG_MULTIUSER */
extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap);
extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap);
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -361,6 +361,24 @@ bool has_capability_noaudit(struct task_
return has_ns_capability_noaudit(t, &init_user_ns, cap);
}
+static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit)
+{
+ int capable;
+
+ if (unlikely(!cap_valid(cap))) {
+ pr_crit("capable() called with invalid cap=%u\n", cap);
+ BUG();
+ }
+
+ capable = audit ? security_capable(current_cred(), ns, cap) :
+ security_capable_noaudit(current_cred(), ns, cap);
+ if (capable == 0) {
+ current->flags |= PF_SUPERPRIV;
+ return true;
+ }
+ return false;
+}
+
/**
* ns_capable - Determine if the current task has a superior capability in effect
* @ns: The usernamespace we want the capability in
@@ -374,19 +392,27 @@ bool has_capability_noaudit(struct task_
*/
bool ns_capable(struct user_namespace *ns, int cap)
{
- if (unlikely(!cap_valid(cap))) {
- pr_crit("capable() called with invalid cap=%u\n", cap);
- BUG();
- }
-
- if (security_capable(current_cred(), ns, cap) == 0) {
- current->flags |= PF_SUPERPRIV;
- return true;
- }
- return false;
+ return ns_capable_common(ns, cap, true);
}
EXPORT_SYMBOL(ns_capable);
+/**
+ * ns_capable_noaudit - Determine if the current task has a superior capability
+ * (unaudited) in effect
+ * @ns: The usernamespace we want the capability in
+ * @cap: The capability to be tested for
+ *
+ * Return true if the current task has the given superior capability currently
+ * available for use, false if not.
+ *
+ * This sets PF_SUPERPRIV on the task if the capability is available on the
+ * assumption that it's about to be used.
+ */
+bool ns_capable_noaudit(struct user_namespace *ns, int cap)
+{
+ return ns_capable_common(ns, cap, false);
+}
+EXPORT_SYMBOL(ns_capable_noaudit);
/**
* capable - Determine if the current task has a superior capability in effect
--
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