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ipc: Store mqueue sysctls in the ipc namespace

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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.

So far, the changes do not provide additional access to files. This will
be done in a future patch.

v3:
* Don't implemenet set_permissions to keep the current behavior.

v2:
* Fixed compilation problem if CONFIG_POSIX_MQUEUE_SYSCTL is not
  specified.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://lkml.kernel.org/r/b0ccbb2489119f1f20c737cf1930c3a9c4e4243a.1644862280.git.legion@kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Alexey Gladkov 2022-02-14 19:18:14 +01:00 committed by Eric W. Biederman
parent ffb217a13a
commit dc55e35f9e
4 changed files with 91 additions and 68 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

16
include/linux/ipc_namespace.h
View file

@ -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 +64,9 @@ struct ipc_namespace {
unsigned int mq_msg_default;
unsigned int mq_msgsize_default;
struct ctl_table_set mq_set;
struct ctl_table_header *mq_sysctls;
/* user_ns which owns the ipc ns */
struct user_namespace *user_ns;
struct ucounts *ucounts;
@ -169,14 +173,18 @@ static inline void put_ipc_ns(struct ipc_namespace *ns)
#ifdef CONFIG_POSIX_MQUEUE_SYSCTL
struct ctl_table_header;
extern struct ctl_table_header *mq_register_sysctl_table(void);
void retire_mq_sysctls(struct ipc_namespace *ns);
bool setup_mq_sysctls(struct ipc_namespace *ns);
#else /* CONFIG_POSIX_MQUEUE_SYSCTL */
static inline struct ctl_table_header *mq_register_sysctl_table(void)
static inline void retire_mq_sysctls(struct ipc_namespace *ns)
{
return NULL;
}
static inline bool setup_mq_sysctls(struct ipc_namespace *ns)
{
return true;
}
#endif /* CONFIG_POSIX_MQUEUE_SYSCTL */

127
ipc/mq_sysctl.c
View file

@ -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 +59,73 @@ 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 mq_sysctl_root[] = {
{
.procname = "fs",
.mode = 0555,
.child = mq_sysctl_dir,
},
{}
};
struct ctl_table_header *mq_register_sysctl_table(void)
static struct ctl_table_set *set_lookup(struct ctl_table_root *root)
{
return register_sysctl_table(mq_sysctl_root);
return &current->nsproxy->ipc_ns->mq_set;
}
static int set_is_seen(struct ctl_table_set *set)
{
return &current->nsproxy->ipc_ns->mq_set == set;
}
static struct ctl_table_root set_root = {
.lookup = set_lookup,
};
bool setup_mq_sysctls(struct ipc_namespace *ns)
{
struct ctl_table *tbl;
setup_sysctl_set(&ns->mq_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->mq_sysctls = __register_sysctl_table(&ns->mq_set, "fs/mqueue", tbl);
}
if (!ns->mq_sysctls) {
kfree(tbl);
retire_sysctl_set(&ns->mq_set);
return false;
}
return true;
}
void retire_mq_sysctls(struct ipc_namespace *ns)
{
struct ctl_table *tbl;
tbl = ns->mq_sysctls->ctl_table_arg;
unregister_sysctl_table(ns->mq_sysctls);
retire_sysctl_set(&ns->mq_set);
kfree(tbl);
}

10
ipc/mqueue.c
View file

@ -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;
}

6
ipc/namespace.c
View file

@ -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);