Right now, the mqueue sysctls take ipc namespaces into account in a
rather hacky way. This works in most cases, but does not respect the
user namespace.
Within the user namespace, the user cannot change the /proc/sys/fs/mqueue/*
parametres. This poses a problem in the rootless containers.
To solve this I changed the implementation of the mqueue sysctls just
like some other sysctls.
Before this change:
$ echo 5 | unshare -r -U -i tee /proc/sys/fs/mqueue/msg_max
tee: /proc/sys/fs/mqueue/msg_max: Permission denied
5
After this change:
$ echo 5 | unshare -r -U -i tee /proc/sys/fs/mqueue/msg_max
5
Signed-off-by: Alexey Gladkov <legion@xxxxxxxxxx>
---
include/linux/ipc_namespace.h | 20 ++---
ipc/mq_sysctl.c | 140 +++++++++++++++++++++-------------
ipc/mqueue.c | 10 +--
ipc/namespace.c | 6 ++
4 files changed, 103 insertions(+), 73 deletions(-)
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index b75395ec8d52..8ecb965905f5 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -10,6 +10,7 @@
#include <linux/ns_common.h>
#include <linux/refcount.h>
#include <linux/rhashtable-types.h>
+#include <linux/sysctl.h>
struct user_namespace;
@@ -63,6 +64,11 @@ struct ipc_namespace {
unsigned int mq_msg_default;
unsigned int mq_msgsize_default;
+#ifdef CONFIG_POSIX_MQUEUE_SYSCTL
+ struct ctl_table_set set;
+ struct ctl_table_header *sysctls;
+#endif
+
/* user_ns which owns the ipc ns */
struct user_namespace *user_ns;
struct ucounts *ucounts;
@@ -167,17 +173,7 @@ static inline void put_ipc_ns(struct ipc_namespace *ns)
}
#endif
-#ifdef CONFIG_POSIX_MQUEUE_SYSCTL
-
-struct ctl_table_header;
-extern struct ctl_table_header *mq_register_sysctl_table(void);
-
-#else /* CONFIG_POSIX_MQUEUE_SYSCTL */
-
-static inline struct ctl_table_header *mq_register_sysctl_table(void)
-{
- return NULL;
-}
+void retire_mq_sysctls(struct ipc_namespace *ns);
+bool setup_mq_sysctls(struct ipc_namespace *ns);
-#endif /* CONFIG_POSIX_MQUEUE_SYSCTL */
#endif
diff --git a/ipc/mq_sysctl.c b/ipc/mq_sysctl.c
index 72a92a08c848..f9826700f08c 100644
--- a/ipc/mq_sysctl.c
+++ b/ipc/mq_sysctl.c
@@ -9,39 +9,9 @@
#include <linux/ipc_namespace.h>
#include <linux/sysctl.h>
-#ifdef CONFIG_PROC_SYSCTL
-static void *get_mq(struct ctl_table *table)
-{
- char *which = table->data;
- struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
- which = (which - (char *)&init_ipc_ns) + (char *)ipc_ns;
- return which;
-}
-
-static int proc_mq_dointvec(struct ctl_table *table, int write,
- void *buffer, size_t *lenp, loff_t *ppos)
-{
- struct ctl_table mq_table;
- memcpy(&mq_table, table, sizeof(mq_table));
- mq_table.data = get_mq(table);
-
- return proc_dointvec(&mq_table, write, buffer, lenp, ppos);
-}
-
-static int proc_mq_dointvec_minmax(struct ctl_table *table, int write,
- void *buffer, size_t *lenp, loff_t *ppos)
-{
- struct ctl_table mq_table;
- memcpy(&mq_table, table, sizeof(mq_table));
- mq_table.data = get_mq(table);
-
- return proc_dointvec_minmax(&mq_table, write, buffer,
- lenp, ppos);
-}
-#else
-#define proc_mq_dointvec NULL
-#define proc_mq_dointvec_minmax NULL
-#endif
+#include <linux/stat.h>
+#include <linux/capability.h>
+#include <linux/slab.h>
static int msg_max_limit_min = MIN_MSGMAX;
static int msg_max_limit_max = HARD_MSGMAX;
@@ -55,14 +25,14 @@ static struct ctl_table mq_sysctls[] = {
.data = &init_ipc_ns.mq_queues_max,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_mq_dointvec,
+ .proc_handler = proc_dointvec,
},
{
.procname = "msg_max",
.data = &init_ipc_ns.mq_msg_max,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_mq_dointvec_minmax,
+ .proc_handler = proc_dointvec_minmax,
.extra1 = &msg_max_limit_min,
.extra2 = &msg_max_limit_max,
},
@@ -71,7 +41,7 @@ static struct ctl_table mq_sysctls[] = {
.data = &init_ipc_ns.mq_msgsize_max,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_mq_dointvec_minmax,
+ .proc_handler = proc_dointvec_minmax,
.extra1 = &msg_maxsize_limit_min,
.extra2 = &msg_maxsize_limit_max,
},
@@ -80,7 +50,7 @@ static struct ctl_table mq_sysctls[] = {
.data = &init_ipc_ns.mq_msg_default,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_mq_dointvec_minmax,
+ .proc_handler = proc_dointvec_minmax,
.extra1 = &msg_max_limit_min,
.extra2 = &msg_max_limit_max,
},
@@ -89,32 +59,92 @@ static struct ctl_table mq_sysctls[] = {
.data = &init_ipc_ns.mq_msgsize_default,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_mq_dointvec_minmax,
+ .proc_handler = proc_dointvec_minmax,
.extra1 = &msg_maxsize_limit_min,
.extra2 = &msg_maxsize_limit_max,
},
{}
};
-static struct ctl_table mq_sysctl_dir[] = {
- {
- .procname = "mqueue",
- .mode = 0555,
- .child = mq_sysctls,
- },
- {}
-};
+static struct ctl_table_set *
+set_lookup(struct ctl_table_root *root)
+{
+ return ¤t->nsproxy->ipc_ns->set;
+}
-static struct ctl_table mq_sysctl_root[] = {
- {
- .procname = "fs",
- .mode = 0555,
- .child = mq_sysctl_dir,
- },
- {}
+static int set_is_seen(struct ctl_table_set *set)
+{
+ return ¤t->nsproxy->ipc_ns->set == set;
+}
+
+static int set_permissions(struct ctl_table_header *head, struct ctl_table *table)
+{
+ struct ipc_namespace *ns = container_of(head->set, struct ipc_namespace, set);
+ int mode;
+
+ /* Allow users with CAP_SYS_RESOURCE unrestrained access */
+ if (ns_capable(ns->user_ns, CAP_SYS_RESOURCE))
+ mode = (table->mode & S_IRWXU) >> 6;
+ else
+ /* Allow all others at most read-only access */
+ mode = table->mode & S_IROTH;
+ return (mode << 6) | (mode << 3) | mode;
+}
+
+static struct ctl_table_root set_root = {
+ .lookup = set_lookup,
+ .permissions = set_permissions,
};
-struct ctl_table_header *mq_register_sysctl_table(void)
+bool setup_mq_sysctls(struct ipc_namespace *ns)
+{
+#ifdef CONFIG_POSIX_MQUEUE_SYSCTL
+ struct ctl_table *tbl;
+
+ setup_sysctl_set(&ns->set, &set_root, set_is_seen);
+
+ tbl = kmemdup(mq_sysctls, sizeof(mq_sysctls), GFP_KERNEL);
+ if (tbl) {
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(mq_sysctls); i++) {
+ if (tbl[i].data == &init_ipc_ns.mq_queues_max)
+ tbl[i].data = &ns->mq_queues_max;
+
+ else if (tbl[i].data == &init_ipc_ns.mq_msg_max)
+ tbl[i].data = &ns->mq_msg_max;
+
+ else if (tbl[i].data == &init_ipc_ns.mq_msgsize_max)
+ tbl[i].data = &ns->mq_msgsize_max;
+
+ else if (tbl[i].data == &init_ipc_ns.mq_msg_default)
+ tbl[i].data = &ns->mq_msg_default;
+
+ else if (tbl[i].data == &init_ipc_ns.mq_msgsize_default)
+ tbl[i].data = &ns->mq_msgsize_default;
+ else
+ tbl[i].data = NULL;
+ }
+
+ ns->sysctls = __register_sysctl_table(&ns->set, "fs/mqueue", tbl);
+ }
+ if (!ns->sysctls) {
+ kfree(tbl);
+ retire_sysctl_set(&ns->set);
+ return false;
+ }
+#endif
+ return true;
+}
+
+void retire_mq_sysctls(struct ipc_namespace *ns)
{
- return register_sysctl_table(mq_sysctl_root);
+#ifdef CONFIG_POSIX_MQUEUE_SYSCTL
+ struct ctl_table *tbl;
+
+ tbl = ns->sysctls->ctl_table_arg;
+ unregister_sysctl_table(ns->sysctls);
+ retire_sysctl_set(&ns->set);
+ kfree(tbl);
+#endif
}
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 5becca9be867..1b4a3be71636 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -163,8 +163,6 @@ static void remove_notification(struct mqueue_inode_info *info);
static struct kmem_cache *mqueue_inode_cachep;
-static struct ctl_table_header *mq_sysctl_table;
-
static inline struct mqueue_inode_info *MQUEUE_I(struct inode *inode)
{
return container_of(inode, struct mqueue_inode_info, vfs_inode);
@@ -1713,8 +1711,10 @@ static int __init init_mqueue_fs(void)
if (mqueue_inode_cachep == NULL)
return -ENOMEM;
- /* ignore failures - they are not fatal */
- mq_sysctl_table = mq_register_sysctl_table();
+ if (!setup_mq_sysctls(&init_ipc_ns)) {
+ pr_warn("sysctl registration failed\n");
+ return -ENOMEM;
+ }
error = register_filesystem(&mqueue_fs_type);
if (error)
@@ -1731,8 +1731,6 @@ static int __init init_mqueue_fs(void)
out_filesystem:
unregister_filesystem(&mqueue_fs_type);
out_sysctl:
- if (mq_sysctl_table)
- unregister_sysctl_table(mq_sysctl_table);
kmem_cache_destroy(mqueue_inode_cachep);
return error;
}
diff --git a/ipc/namespace.c b/ipc/namespace.c
index ae83f0f2651b..f760243ca685 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -59,6 +59,10 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
if (err)
goto fail_put;
+ err = -ENOMEM;
+ if (!setup_mq_sysctls(ns))
+ goto fail_put;
+
sem_init_ns(ns);
msg_init_ns(ns);
shm_init_ns(ns);
@@ -125,6 +129,8 @@ static void free_ipc_ns(struct ipc_namespace *ns)
msg_exit_ns(ns);
shm_exit_ns(ns);
+ retire_mq_sysctls(ns);
+
dec_ipc_namespaces(ns->ucounts);
put_user_ns(ns->user_ns);
ns_free_inum(&ns->ns);
--
2.33.0
