[PATCH] net: Use ns_capable_noaudit() when determining net sysctl permissions

From: Dmitry Torokhov
Date: Fri Sep 30 2016 - 18:24:59 EST

From: Tyler Hicks <tyhicks@xxxxxxxxxxxxx>

The capability check should not be audited since it is only being used
to determine the inode permissions. A failed check does not indicate a
violation of security policy but, when an LSM is enabled, a denial audit
message was being generated.

The denial audit message caused confusion for some application authors
because root-running Go applications always triggered the denial. To
prevent this confusion, the capability check in net_ctl_permissions() is
switched to the noaudit variant.

BugLink: https://launchpad.net/bugs/1465724

Signed-off-by: Tyler Hicks <tyhicks@xxxxxxxxxxxxx>
Acked-by: Serge E. Hallyn <serge.hallyn@xxxxxxxxxx>
Signed-off-by: James Morris <james.l.morris@xxxxxxxxxx>
[dtor: reapplied after e79c6a4fc923 ("net: make net namespace sysctls
belong to container's owner") accidentally reverted the change.]
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
net/sysctl_net.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sysctl_net.c b/net/sysctl_net.c
index c5d37f4..9199813 100644
--- a/net/sysctl_net.c
+++ b/net/sysctl_net.c
@@ -44,7 +44,7 @@ static int net_ctl_permissions(struct ctl_table_header *head,
struct net *net = container_of(head->set, struct net, sysctls);

/* Allow network administrator to have same access as root. */
- if (ns_capable(net->user_ns, CAP_NET_ADMIN)) {
+ if (ns_capable_noaudit(net->user_ns, CAP_NET_ADMIN)) {
int mode = (table->mode >> 6) & 7;
return (mode << 6) | (mode << 3) | mode;