The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 7a0cf094944e2540758b7f957eb6846d5126f535 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" ebiederm@xmission.com Date: Wed, 15 May 2019 22:54:56 -0500 Subject: [PATCH] signal: Correct namespace fixups of si_pid and si_uid
The function send_signal was split from __send_signal so that it would be possible to bypass the namespace logic based upon current[1]. As it turns out the si_pid and the si_uid fixup are both inappropriate in the case of kill_pid_usb_asyncio so move that logic into send_signal.
It is difficult to arrange but possible for a signal with an si_code of SI_TIMER or SI_SIGIO to be sent across namespace boundaries. In which case tests for when it is ok to change si_pid and si_uid based on SI_FROMUSER are incorrect. Replace the use of SI_FROMUSER with a new test has_si_pid_and_used based on siginfo_layout.
Now that the uid fixup is no longer present after expanding SEND_SIG_NOINFO properly calculate the si_uid that the target task needs to read.
[1] 7978b567d315 ("signals: add from_ancestor_ns parameter to send_signal()") Cc: stable@vger.kernel.org Fixes: 6588c1e3ff01 ("signals: SI_USER: Masquerade si_pid when crossing pid ns boundary") Fixes: 6b550f949594 ("user namespace: make signal.c respect user namespaces") Signed-off-by: "Eric W. Biederman" ebiederm@xmission.com
diff --git a/kernel/signal.c b/kernel/signal.c index 18040d6bd63a..39a3eca5ce22 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1056,27 +1056,6 @@ static inline bool legacy_queue(struct sigpending *signals, int sig) return (sig < SIGRTMIN) && sigismember(&signals->signal, sig); }
-#ifdef CONFIG_USER_NS -static inline void userns_fixup_signal_uid(struct kernel_siginfo *info, struct task_struct *t) -{ - if (current_user_ns() == task_cred_xxx(t, user_ns)) - return; - - if (SI_FROMKERNEL(info)) - return; - - rcu_read_lock(); - info->si_uid = from_kuid_munged(task_cred_xxx(t, user_ns), - make_kuid(current_user_ns(), info->si_uid)); - rcu_read_unlock(); -} -#else -static inline void userns_fixup_signal_uid(struct kernel_siginfo *info, struct task_struct *t) -{ - return; -} -#endif - static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struct *t, enum pid_type type, int from_ancestor_ns) { @@ -1134,7 +1113,11 @@ static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struc q->info.si_code = SI_USER; q->info.si_pid = task_tgid_nr_ns(current, task_active_pid_ns(t)); - q->info.si_uid = from_kuid_munged(current_user_ns(), current_uid()); + rcu_read_lock(); + q->info.si_uid = + from_kuid_munged(task_cred_xxx(t, user_ns), + current_uid()); + rcu_read_unlock(); break; case (unsigned long) SEND_SIG_PRIV: clear_siginfo(&q->info); @@ -1146,13 +1129,8 @@ static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struc break; default: copy_siginfo(&q->info, info); - if (from_ancestor_ns) - q->info.si_pid = 0; break; } - - userns_fixup_signal_uid(&q->info, t); - } else if (!is_si_special(info)) { if (sig >= SIGRTMIN && info->si_code != SI_USER) { /* @@ -1196,6 +1174,28 @@ static int __send_signal(int sig, struct kernel_siginfo *info, struct task_struc return ret; }
+static inline bool has_si_pid_and_uid(struct kernel_siginfo *info) +{ + bool ret = false; + switch (siginfo_layout(info->si_signo, info->si_code)) { + case SIL_KILL: + case SIL_CHLD: + case SIL_RT: + ret = true; + break; + case SIL_TIMER: + case SIL_POLL: + case SIL_FAULT: + case SIL_FAULT_MCEERR: + case SIL_FAULT_BNDERR: + case SIL_FAULT_PKUERR: + case SIL_SYS: + ret = false; + break; + } + return ret; +} + static int send_signal(int sig, struct kernel_siginfo *info, struct task_struct *t, enum pid_type type) { @@ -1205,7 +1205,20 @@ static int send_signal(int sig, struct kernel_siginfo *info, struct task_struct from_ancestor_ns = si_fromuser(info) && !task_pid_nr_ns(current, task_active_pid_ns(t)); #endif + if (!is_si_special(info) && has_si_pid_and_uid(info)) { + struct user_namespace *t_user_ns;
+ rcu_read_lock(); + t_user_ns = task_cred_xxx(t, user_ns); + if (current_user_ns() != t_user_ns) { + kuid_t uid = make_kuid(current_user_ns(), info->si_uid); + info->si_uid = from_kuid_munged(t_user_ns, uid); + } + rcu_read_unlock(); + + if (!task_pid_nr_ns(current, task_active_pid_ns(t))) + info->si_pid = 0; + } return __send_signal(sig, info, t, type, from_ancestor_ns); }