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authorEric W. Biederman <ebiederm@xmission.com>2019-05-15 22:54:56 -0500
committerEric W. Biederman <ebiederm@xmission.com>2019-05-22 17:02:16 -0500
commit7a0cf094944e2540758b7f957eb6846d5126f535 (patch)
tree7bf6f9b6aed7c10d437f7de78b49090b72c7e7a4 /kernel/signal.c
parent70f1b0d34bdf03065fe869e93cc17cad1ea20c4a (diff)
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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>
Diffstat (limited to 'kernel/signal.c')
-rw-r--r--kernel/signal.c67
1 files changed, 40 insertions, 27 deletions
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 @@ ret:
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);
}