From bbe660db23e41647366039c1860cee0891fe9903 Mon Sep 17 00:00:00 2001 From: Jamie Iles Date: Tue, 10 Jan 2017 16:57:54 -0800 Subject: signal: protect SIGNAL_UNKILLABLE from unintentional clearing. [ Upstream commit 2d39b3cd34e6d323720d4c61bd714f5ae202c022 ] Since commit 00cd5c37afd5 ("ptrace: permit ptracing of /sbin/init") we can now trace init processes. init is initially protected with SIGNAL_UNKILLABLE which will prevent fatal signals such as SIGSTOP, but there are a number of paths during tracing where SIGNAL_UNKILLABLE can be implicitly cleared. This can result in init becoming stoppable/killable after tracing. For example, running: while true; do kill -STOP 1; done & strace -p 1 and then stopping strace and the kill loop will result in init being left in state TASK_STOPPED. Sending SIGCONT to init will resume it, but init will now respond to future SIGSTOP signals rather than ignoring them. Make sure that when setting SIGNAL_STOP_CONTINUED/SIGNAL_STOP_STOPPED that we don't clear SIGNAL_UNKILLABLE. Link: http://lkml.kernel.org/r/20170104122017.25047-1-jamie.iles@oracle.com Signed-off-by: Jamie Iles Acked-by: Oleg Nesterov Cc: Alexander Viro Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- include/linux/sched.h | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include/linux/sched.h') diff --git a/include/linux/sched.h b/include/linux/sched.h index 352213b360d7..eff7c1fad26f 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -801,6 +801,16 @@ struct signal_struct { #define SIGNAL_UNKILLABLE 0x00000040 /* for init: ignore fatal signals */ +#define SIGNAL_STOP_MASK (SIGNAL_CLD_MASK | SIGNAL_STOP_STOPPED | \ + SIGNAL_STOP_CONTINUED) + +static inline void signal_set_stop_flags(struct signal_struct *sig, + unsigned int flags) +{ + WARN_ON(sig->flags & (SIGNAL_GROUP_EXIT|SIGNAL_GROUP_COREDUMP)); + sig->flags = (sig->flags & ~SIGNAL_STOP_MASK) | flags; +} + /* If true, all threads except ->group_exit_task have pending SIGKILL */ static inline int signal_group_exit(const struct signal_struct *sig) { -- cgit v1.2.3 From b4cf49024cf412a94121e61f8056636c557ead98 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 21 Aug 2017 17:35:02 +0200 Subject: pids: make task_tgid_nr_ns() safe commit dd1c1f2f2028a7b851f701fc6a8ebe39dcb95e7c upstream. This was reported many times, and this was even mentioned in commit 52ee2dfdd4f5 ("pids: refactor vnr/nr_ns helpers to make them safe") but somehow nobody bothered to fix the obvious problem: task_tgid_nr_ns() is not safe because task->group_leader points to nowhere after the exiting task passes exit_notify(), rcu_read_lock() can not help. We really need to change __unhash_process() to nullify group_leader, parent, and real_parent, but this needs some cleanups. Until then we can turn task_tgid_nr_ns() into another user of __task_pid_nr_ns() and fix the problem. Reported-by: Troy Kensinger Signed-off-by: Oleg Nesterov Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- include/linux/sched.h | 50 +++++++++++++++++++++++++++----------------------- 1 file changed, 27 insertions(+), 23 deletions(-) (limited to 'include/linux/sched.h') diff --git a/include/linux/sched.h b/include/linux/sched.h index eff7c1fad26f..e887c8d6f395 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1949,31 +1949,8 @@ static inline pid_t task_tgid_nr(struct task_struct *tsk) return tsk->tgid; } -pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns); - -static inline pid_t task_tgid_vnr(struct task_struct *tsk) -{ - return pid_vnr(task_tgid(tsk)); -} - static inline int pid_alive(const struct task_struct *p); -static inline pid_t task_ppid_nr_ns(const struct task_struct *tsk, struct pid_namespace *ns) -{ - pid_t pid = 0; - - rcu_read_lock(); - if (pid_alive(tsk)) - pid = task_tgid_nr_ns(rcu_dereference(tsk->real_parent), ns); - rcu_read_unlock(); - - return pid; -} - -static inline pid_t task_ppid_nr(const struct task_struct *tsk) -{ - return task_ppid_nr_ns(tsk, &init_pid_ns); -} static inline pid_t task_pgrp_nr_ns(struct task_struct *tsk, struct pid_namespace *ns) @@ -1998,6 +1975,33 @@ static inline pid_t task_session_vnr(struct task_struct *tsk) return __task_pid_nr_ns(tsk, PIDTYPE_SID, NULL); } +static inline pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns) +{ + return __task_pid_nr_ns(tsk, __PIDTYPE_TGID, ns); +} + +static inline pid_t task_tgid_vnr(struct task_struct *tsk) +{ + return __task_pid_nr_ns(tsk, __PIDTYPE_TGID, NULL); +} + +static inline pid_t task_ppid_nr_ns(const struct task_struct *tsk, struct pid_namespace *ns) +{ + pid_t pid = 0; + + rcu_read_lock(); + if (pid_alive(tsk)) + pid = task_tgid_nr_ns(rcu_dereference(tsk->real_parent), ns); + rcu_read_unlock(); + + return pid; +} + +static inline pid_t task_ppid_nr(const struct task_struct *tsk) +{ + return task_ppid_nr_ns(tsk, &init_pid_ns); +} + /* obsolete, do not use */ static inline pid_t task_pgrp_nr(struct task_struct *tsk) { -- cgit v1.2.3