From 42815808f1791eb53c3a05fb78c0a8642ecf8467 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Mon, 6 Jul 2020 17:49:09 +0200 Subject: timens: make vdso_join_timens() always succeed As discussed on-list (cf. [1]), in order to make setns() support time namespaces when attaching to multiple namespaces at once properly we need to tweak vdso_join_timens() to always succeed. So switch vdso_join_timens() to using a read lock and replacing mmap_write_lock_killable() to mmap_read_lock() as we discussed. Last cycle setns() was changed to support attaching to multiple namespaces atomically. This requires all namespaces to have a point of no return where they can't fail anymore. Specifically, _install() is allowed to perform permission checks and install the namespace into the new struct nsset that it has been given but it is not allowed to make visible changes to the affected task. Once _install() returns anything that the given namespace type requires to be setup in addition needs to ideally be done in a function that can't fail or if it fails the failure is not fatal. For time namespaces the relevant functions that fall into this category are timens_set_vvar_page() and vdso_join_timens(). Currently the latter can fail but doesn't need to. With this we can go on to implement a timens_commit() helper in a follow up patch to be used by setns(). [1]: https://lore.kernel.org/lkml/20200611110221.pgd3r5qkjrjmfqa2@wittgenstein Signed-off-by: Christian Brauner Reviewed-by: Andrei Vagin Cc: Will Deacon Cc: Vincenzo Frascino Cc: Thomas Gleixner Cc: Andy Lutomirski Cc: Catalin Marinas Cc: Mark Rutland Cc: Dmitry Safonov Cc: linux-arm-kernel@lists.infradead.org Link: https://lore.kernel.org/r/20200706154912.3248030-2-christian.brauner@ubuntu.com --- kernel/time/namespace.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) (limited to 'kernel') diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c index 5d9fc22d836a..e5af6fe87af8 100644 --- a/kernel/time/namespace.c +++ b/kernel/time/namespace.c @@ -284,7 +284,6 @@ static int timens_install(struct nsset *nsset, struct ns_common *new) { struct nsproxy *nsproxy = nsset->nsproxy; struct time_namespace *ns = to_time_ns(new); - int err; if (!current_is_single_threaded()) return -EUSERS; @@ -295,9 +294,7 @@ static int timens_install(struct nsset *nsset, struct ns_common *new) timens_set_vvar_page(current, ns); - err = vdso_join_timens(current, ns); - if (err) - return err; + vdso_join_timens(current, ns); get_time_ns(ns); put_time_ns(nsproxy->time_ns); @@ -313,7 +310,6 @@ int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk) { struct ns_common *nsc = &nsproxy->time_ns_for_children->ns; struct time_namespace *ns = to_time_ns(nsc); - int err; /* create_new_namespaces() already incremented the ref counter */ if (nsproxy->time_ns == nsproxy->time_ns_for_children) @@ -321,9 +317,7 @@ int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk) timens_set_vvar_page(tsk, ns); - err = vdso_join_timens(tsk, ns); - if (err) - return err; + vdso_join_timens(tsk, ns); get_time_ns(ns); put_time_ns(nsproxy->time_ns); -- cgit v1.2.3 From 5cfea9a106bbb1af919ab94456fdd02209984070 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Mon, 6 Jul 2020 17:49:10 +0200 Subject: timens: add timens_commit() helper Wrap the calls to timens_set_vvar_page() and vdso_join_timens() in timens_on_fork() and timens_install() in a new timens_commit() helper. We'll use this helper in a follow-up patch in nsproxy too. Signed-off-by: Christian Brauner Reviewed-by: Andrei Vagin Cc: Will Deacon Cc: Vincenzo Frascino Cc: Thomas Gleixner Cc: Catalin Marinas Cc: Mark Rutland Cc: Dmitry Safonov Cc: linux-arm-kernel@lists.infradead.org Link: https://lore.kernel.org/r/20200706154912.3248030-3-christian.brauner@ubuntu.com --- kernel/time/namespace.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) (limited to 'kernel') diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c index e5af6fe87af8..aa7b90aac2a7 100644 --- a/kernel/time/namespace.c +++ b/kernel/time/namespace.c @@ -280,6 +280,12 @@ static void timens_put(struct ns_common *ns) put_time_ns(to_time_ns(ns)); } +static void timens_commit(struct task_struct *tsk, struct time_namespace *ns) +{ + timens_set_vvar_page(tsk, ns); + vdso_join_timens(tsk, ns); +} + static int timens_install(struct nsset *nsset, struct ns_common *new) { struct nsproxy *nsproxy = nsset->nsproxy; @@ -292,9 +298,8 @@ static int timens_install(struct nsset *nsset, struct ns_common *new) !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN)) return -EPERM; - timens_set_vvar_page(current, ns); - vdso_join_timens(current, ns); + timens_commit(current, ns); get_time_ns(ns); put_time_ns(nsproxy->time_ns); @@ -315,14 +320,12 @@ int timens_on_fork(struct nsproxy *nsproxy, struct task_struct *tsk) if (nsproxy->time_ns == nsproxy->time_ns_for_children) return 0; - timens_set_vvar_page(tsk, ns); - - vdso_join_timens(tsk, ns); - get_time_ns(ns); put_time_ns(nsproxy->time_ns); nsproxy->time_ns = ns; + timens_commit(tsk, ns); + return 0; } -- cgit v1.2.3 From 76c12881a38aaa83e1eb4ce2fada36c3a732bad4 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Mon, 6 Jul 2020 17:49:11 +0200 Subject: nsproxy: support CLONE_NEWTIME with setns() So far setns() was missing time namespace support. This was partially due to it simply not being implemented but also because vdso_join_timens() could still fail which made switching to multiple namespaces atomically problematic. This is now fixed so support CLONE_NEWTIME with setns() Signed-off-by: Christian Brauner Reviewed-by: Andrei Vagin Cc: Thomas Gleixner Cc: Michael Kerrisk Cc: Serge Hallyn Cc: Dmitry Safonov Link: https://lore.kernel.org/r/20200706154912.3248030-4-christian.brauner@ubuntu.com --- include/linux/time_namespace.h | 6 ++++++ kernel/nsproxy.c | 21 +++++++++++++++++++-- kernel/time/namespace.c | 5 +---- 3 files changed, 26 insertions(+), 6 deletions(-) (limited to 'kernel') diff --git a/include/linux/time_namespace.h b/include/linux/time_namespace.h index 824d54e057eb..5b6031385db0 100644 --- a/include/linux/time_namespace.h +++ b/include/linux/time_namespace.h @@ -33,6 +33,7 @@ extern struct time_namespace init_time_ns; #ifdef CONFIG_TIME_NS extern int vdso_join_timens(struct task_struct *task, struct time_namespace *ns); +extern void timens_commit(struct task_struct *tsk, struct time_namespace *ns); static inline struct time_namespace *get_time_ns(struct time_namespace *ns) { @@ -96,6 +97,11 @@ static inline int vdso_join_timens(struct task_struct *task, return 0; } +static inline void timens_commit(struct task_struct *tsk, + struct time_namespace *ns) +{ +} + static inline struct time_namespace *get_time_ns(struct time_namespace *ns) { return NULL; diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c index cd356630a311..12dd41b39a7f 100644 --- a/kernel/nsproxy.c +++ b/kernel/nsproxy.c @@ -262,8 +262,8 @@ void exit_task_namespaces(struct task_struct *p) static int check_setns_flags(unsigned long flags) { if (!flags || (flags & ~(CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC | - CLONE_NEWNET | CLONE_NEWUSER | CLONE_NEWPID | - CLONE_NEWCGROUP))) + CLONE_NEWNET | CLONE_NEWTIME | CLONE_NEWUSER | + CLONE_NEWPID | CLONE_NEWCGROUP))) return -EINVAL; #ifndef CONFIG_USER_NS @@ -290,6 +290,10 @@ static int check_setns_flags(unsigned long flags) if (flags & CLONE_NEWNET) return -EINVAL; #endif +#ifndef CONFIG_TIME_NS + if (flags & CLONE_NEWTIME) + return -EINVAL; +#endif return 0; } @@ -464,6 +468,14 @@ static int validate_nsset(struct nsset *nsset, struct pid *pid) } #endif +#ifdef CONFIG_TIME_NS + if (flags & CLONE_NEWTIME) { + ret = validate_ns(nsset, &nsp->time_ns->ns); + if (ret) + goto out; + } +#endif + out: if (pid_ns) put_pid_ns(pid_ns); @@ -507,6 +519,11 @@ static void commit_nsset(struct nsset *nsset) exit_sem(me); #endif +#ifdef CONFIG_TIME_NS + if (flags & CLONE_NEWTIME) + timens_commit(me, nsset->nsproxy->time_ns); +#endif + /* transfer ownership */ switch_task_namespaces(me, nsset->nsproxy); nsset->nsproxy = NULL; diff --git a/kernel/time/namespace.c b/kernel/time/namespace.c index aa7b90aac2a7..afc65e6be33e 100644 --- a/kernel/time/namespace.c +++ b/kernel/time/namespace.c @@ -280,7 +280,7 @@ static void timens_put(struct ns_common *ns) put_time_ns(to_time_ns(ns)); } -static void timens_commit(struct task_struct *tsk, struct time_namespace *ns) +void timens_commit(struct task_struct *tsk, struct time_namespace *ns) { timens_set_vvar_page(tsk, ns); vdso_join_timens(tsk, ns); @@ -298,9 +298,6 @@ static int timens_install(struct nsset *nsset, struct ns_common *new) !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN)) return -EPERM; - - timens_commit(current, ns); - get_time_ns(ns); put_time_ns(nsproxy->time_ns); nsproxy->time_ns = ns; -- cgit v1.2.3