[PATCH v2] net: qrtr: Expand control port access to root

[Vishnu Santhosh]

When qrtr is loaded as module, QRTR NS runs from SELinux kmod_t
domain. On targets using upstream SELinux policies, this domain
does not receive CAP_NET_ADMIN, which prevents it from binding
control port even though QRTR NS is a trusted system component.

Granting kmod_t the CAP_NET_ADMIN capability in policy is possible,
but not desirable, as kmod_t is not expected to perform networking
operations and widening its capability set is discouraged.

To address this in a contained way within qrtr, extend the control
port permission check to allow binding when either:

  - the process has CAP_NET_ADMIN, or
  - the process belongs to GLOBAL_ROOT_GID (root-equivalent tasks)

This permits QRTR NS to successfully bind its control port in
kmod_t restricted environments without broadening SELinux capability
assignments.

Co-developed-by: Deepak Kumar Singh <deepak.singh@xxxxxxxxxxxxxxxx>
Signed-off-by: Deepak Kumar Singh <deepak.singh@xxxxxxxxxxxxxxxx>
Signed-off-by: Vishnu Santhosh <vishnu.santhosh@xxxxxxxxxxxxxxxx>
---
Changes in v2:
- Replaced "qrtr-ns" with "QRTR NS" in the commit message to avoid
  confusion with the deprecated userspace qrtr-ns tool and the NS
  implementation inside the QRTR driver.
- Link to v1: https://lore.kernel.org/r/20260205-qrtr-control-port-access-permission-v1-1-e900039e92d5@xxxxxxxxxxxxxxxx
---
 net/qrtr/af_qrtr.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/qrtr/af_qrtr.c b/net/qrtr/af_qrtr.c
index dab839f61ee93b876021d904ae6b8dca8ed43745..b0e252c16f156c05973988fbdf317a149ad9840d 100644
--- a/net/qrtr/af_qrtr.c
+++ b/net/qrtr/af_qrtr.c
@@ -8,6 +8,7 @@
 #include <linux/qrtr.h>
 #include <linux/termios.h>	/* For TIOCINQ/OUTQ */
 #include <linux/spinlock.h>
+#include <linux/uidgid.h>
 #include <linux/wait.h>
 
 #include <net/sock.h>
@@ -738,7 +739,8 @@ static int qrtr_port_assign(struct qrtr_sock *ipc, int *port)
 	if (!*port) {
 		rc = xa_alloc(&qrtr_ports, port, ipc, QRTR_EPH_PORT_RANGE,
 				GFP_KERNEL);
-	} else if (*port < QRTR_MIN_EPH_SOCKET && !capable(CAP_NET_ADMIN)) {
+	} else if (*port < QRTR_MIN_EPH_SOCKET && !(capable(CAP_NET_ADMIN) ||
+						   in_egroup_p(GLOBAL_ROOT_GID))) {
 		rc = -EACCES;
 	} else if (*port == QRTR_PORT_CTRL) {
 		rc = xa_insert(&qrtr_ports, 0, ipc, GFP_KERNEL);

---
base-commit: 0f2acd3148e0ef42bdacbd477f90e8533f96b2ac
change-id: 20260205-qrtr-control-port-access-permission-bfea19994a58

Best regards,
-- 
Vishnu Santhosh <vishnu.santhosh@xxxxxxxxxxxxxxxx>