Messages in this thread | | | Date | Mon, 13 Sep 2021 16:40:47 +0200 | From | Christian Brauner <> | Subject | Re: [PATCH V2] ipc: add set_ownership() and permissions() callbacks for posix mqueue sysctl |
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On Fri, Aug 27, 2021 at 03:12:06AM -0700, CGEL wrote: > From: Ran Xiaokai <ran.xiaokai@zte.com.cn> > > When a non-root user process creates a user namespace and ipc namespace > with command "unshare -Ur -i", and map the root user inside > the user namesapce to the global owner of user namespace. > The newly created user namespace OWNS the ipc namespace, > So the root user inside the user namespace should have full access > rights to the ipc namespace resources and should be writable to > the ipc mqueue sysctls. > > v2: > - update commit msg. > - fix the coding style issue. > Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn> > ---
David,
are you happy with this too? If so I'd pick this up.
> include/linux/ipc_namespace.h | 14 +++++ > ipc/mq_sysctl.c | 118 ++++++++++++++++++++++++++++++++++++------ > ipc/mqueue.c | 10 +++- > ipc/namespace.c | 2 + > 4 files changed, 126 insertions(+), 18 deletions(-) > > diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h > index 05e2277..3e8e340 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; > > @@ -67,6 +68,11 @@ struct ipc_namespace { > struct user_namespace *user_ns; > struct ucounts *ucounts; > > +#ifdef CONFIG_POSIX_MQUEUE_SYSCTL > + struct ctl_table_set mq_set; > + struct ctl_table_header *sysctls; > +#endif > + > struct llist_node mnt_llist; > > struct ns_common ns; > @@ -155,7 +161,10 @@ 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_sysctl_table; > extern struct ctl_table_header *mq_register_sysctl_table(void); > +bool setup_mq_sysctls(struct ipc_namespace *ns); > +void retire_mq_sysctls(struct ipc_namespace *ns); > > #else /* CONFIG_POSIX_MQUEUE_SYSCTL */ > > @@ -163,6 +172,11 @@ static inline struct ctl_table_header *mq_register_sysctl_table(void) > { > return NULL; > } > +static inline bool setup_mq_sysctls(struct ipc_namespace *ns) > +{ > + return true; > +} > +static inline void retire_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 72a92a0..8d6b8ff 100644 > --- a/ipc/mq_sysctl.c > +++ b/ipc/mq_sysctl.c > @@ -8,6 +8,11 @@ > #include <linux/nsproxy.h> > #include <linux/ipc_namespace.h> > #include <linux/sysctl.h> > +#include <linux/slab.h> > +#include <linux/user_namespace.h> > +#include <linux/capability.h> > +#include <linux/cred.h> > +#include <linux/stat.h> > > #ifdef CONFIG_PROC_SYSCTL > static void *get_mq(struct ctl_table *table) > @@ -96,25 +101,106 @@ static struct ctl_table mq_sysctls[] = { > {} > }; > > -static struct ctl_table mq_sysctl_dir[] = { > - { > - .procname = "mqueue", > - .mode = 0555, > - .child = mq_sysctls, > - }, > - {} > -}; > +static int set_is_seen(struct ctl_table_set *set) > +{ > + return ¤t->nsproxy->ipc_ns->mq_set == set; > +} > > -static struct ctl_table mq_sysctl_root[] = { > - { > - .procname = "fs", > - .mode = 0555, > - .child = mq_sysctl_dir, > - }, > - {} > +static struct ctl_table_set * > +set_lookup(struct ctl_table_root *root) > +{ > + return ¤t->nsproxy->ipc_ns->mq_set; > +} > + > +static int set_permissions(struct ctl_table_header *head, > + struct ctl_table *table) > +{ > + struct ipc_namespace *ipc_ns = > + container_of(head->set, struct ipc_namespace, mq_set); > + struct user_namespace *user_ns = ipc_ns->user_ns; > + int mode; > + > + /* Allow users with CAP_SYS_RESOURCE unrestrained access */ > + if (ns_capable(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 void set_ownership(struct ctl_table_header *head, > + struct ctl_table *table, > + kuid_t *uid, kgid_t *gid) > +{ > + struct ipc_namespace *ipc_ns = > + container_of(head->set, struct ipc_namespace, mq_set); > + struct user_namespace *user_ns = ipc_ns->user_ns; > + kuid_t ns_root_uid; > + kgid_t ns_root_gid; > + > + ns_root_uid = make_kuid(user_ns, 0); > + if (uid_valid(ns_root_uid)) > + *uid = ns_root_uid; > + > + ns_root_gid = make_kgid(user_ns, 0); > + if (gid_valid(ns_root_gid)) > + *gid = ns_root_gid; > +} > + > +static struct ctl_table_root mq_sysctl_root = { > + .lookup = set_lookup, > + .permissions = set_permissions, > + .set_ownership = set_ownership, > }; > > +bool setup_mq_sysctls(struct ipc_namespace *ns) > +{ > + struct ctl_table *tbl; > + > + if (!mq_sysctl_table) > + return false; > + > + setup_sysctl_set(&ns->mq_set, &mq_sysctl_root, set_is_seen); > + tbl = kmemdup(mq_sysctls, sizeof(mq_sysctls), GFP_KERNEL); > + if (!tbl) > + goto out; > + > + ns->sysctls = __register_sysctl_table(&ns->mq_set, "fs/mqueue", tbl); > + if (!ns->sysctls) > + goto out1; > + > + return true; > + > +out1: > + kfree(tbl); > + retire_sysctl_set(&ns->mq_set); > +out: > + return false; > +} > + > +void retire_mq_sysctls(struct ipc_namespace *ns) > +{ > + struct ctl_table *tbl; > + > + if (!ns->sysctls) > + return; > + > + tbl = ns->sysctls->ctl_table_arg; > + unregister_sysctl_table(ns->sysctls); > + retire_sysctl_set(&ns->mq_set); > + kfree(tbl); > +} > + > struct ctl_table_header *mq_register_sysctl_table(void) > { > - return register_sysctl_table(mq_sysctl_root); > + static struct ctl_table empty[1]; > + > + /* > + * Register the fs/mqueue directory in the default set so that > + * registrations in the child sets work properly. > + */ > + return register_sysctl("fs/mqueue", empty); > } > diff --git a/ipc/mqueue.c b/ipc/mqueue.c > index 4e4e611..3b68564 100644 > --- a/ipc/mqueue.c > +++ b/ipc/mqueue.c > @@ -163,7 +163,7 @@ static void remove_notification(struct mqueue_inode_info *info); > > static struct kmem_cache *mqueue_inode_cachep; > > -static struct ctl_table_header *mq_sysctl_table; > +struct ctl_table_header *mq_sysctl_table; > > static inline struct mqueue_inode_info *MQUEUE_I(struct inode *inode) > { > @@ -1713,6 +1713,10 @@ static int __init init_mqueue_fs(void) > > /* ignore failures - they are not fatal */ > mq_sysctl_table = mq_register_sysctl_table(); > + if (mq_sysctl_table && !setup_mq_sysctls(&init_ipc_ns)) { > + unregister_sysctl_table(mq_sysctl_table); > + mq_sysctl_table = NULL; > + } > > error = register_filesystem(&mqueue_fs_type); > if (error) > @@ -1729,8 +1733,10 @@ static int __init init_mqueue_fs(void) > out_filesystem: > unregister_filesystem(&mqueue_fs_type); > out_sysctl: > - if (mq_sysctl_table) > + if (mq_sysctl_table) { > + retire_mq_sysctls(&init_ipc_ns); > 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 7bd0766..c891cc1 100644 > --- a/ipc/namespace.c > +++ b/ipc/namespace.c > @@ -58,6 +58,7 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns, > err = mq_init_ns(ns); > if (err) > goto fail_put; > + setup_mq_sysctls(ns); > > sem_init_ns(ns); > msg_init_ns(ns); > @@ -121,6 +122,7 @@ static void free_ipc_ns(struct ipc_namespace *ns) > * uses synchronize_rcu(). > */ > mq_put_mnt(ns); > + retire_mq_sysctls(ns); > sem_exit_ns(ns); > msg_exit_ns(ns); > shm_exit_ns(ns); > -- > 2.15.2 >
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