[PATCH v1] sysctl: Allow change system v ipc sysctls inside ipc namespace

Rootless containers are not allowed to modify kernel IPC parameters such
as kernel.msgmnb.

It seems to me that we can allow customization of these parameters if
the user has CAP_SYS_RESOURCE in that ipc namespace.

CAP_SYS_RESOURCE is already needed in order to overcome mqueue limits
(msg_max and msgsize_max).

Signed-off-by: Alexey Gladkov <[email protected]>
---
 ipc/ipc_sysctl.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
index ef313ecfb53a..e79452867720 100644
--- a/ipc/ipc_sysctl.c
+++ b/ipc/ipc_sysctl.c
@@ -193,16 +193,19 @@ static int set_is_seen(struct ctl_table_set *set)
 static int ipc_permissions(struct ctl_table_header *head, struct ctl_table *table)
 {
 	int mode = table->mode;
-
-#ifdef CONFIG_CHECKPOINT_RESTORE
 	struct ipc_namespace *ns = current->nsproxy->ipc_ns;
 
+#ifdef CONFIG_CHECKPOINT_RESTORE
 	if (((table->data == &ns->ids[IPC_SEM_IDS].next_id) ||
 	     (table->data == &ns->ids[IPC_MSG_IDS].next_id) ||
 	     (table->data == &ns->ids[IPC_SHM_IDS].next_id)) &&
 	    checkpoint_restore_ns_capable(ns->user_ns))
 		mode = 0666;
+	else
 #endif
+	if (ns_capable(ns->user_ns, CAP_SYS_RESOURCE))
+		mode = 0666;
+
 	return mode;
 }
 
-- 
2.33.3