From: Sukadev Bhattiprolu <[email protected]>
Subject: [RFC][PATCH 4/7][v4] Protect cinit from unblocked SIG_DFL signals
Drop early any SIG_DFL or SIG_IGN signals to container-init from within
the same container. But queue SIGSTOP and SIGKILL to the container-init
if they are from an ancestor container.
Blocked, fatal signals (i.e when SIG_DFL is to terminate) from within the
container can still terminate the container-init. That will be addressed
in the next patch.
Note: To be bisect-safe, SIGNAL_UNKILLABLE will be set for container-inits
in a follow-on patch. Until then, this patch is just a preparatory
setp.
Changelog[v2]:
- (Oleg Nesterov) Remove SIGNAL_UNKILLABLE_FROM_NS and rename
'same_ns' to 'from_ancestor_ns'.
- SIGNAL_UNKILLABLE is not yet set for container-inits (will be
set in follow-on patch).
Signed-off-by: Sukadev Bhattiprolu <[email protected]>
---
kernel/signal.c | 36 +++++++++++++++++++++++++++---------
1 files changed, 27 insertions(+), 9 deletions(-)
diff --git a/kernel/signal.c b/kernel/signal.c
index 0011f99..5c4374f 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -53,20 +53,34 @@ static int sig_handler_ignored(void __user *handler, int
sig)
(handler == SIG_DFL && sig_kernel_ignore(sig));
}
-static int sig_task_ignored(struct task_struct *t, int sig)
+/*
+ * Return 1 if task @t is either the global init or the container-init
+ * of the sender's container. Return 0 otherwise.
+ */
+static int sig_task_unkillable(struct task_struct *t, int from_ancestor_ns)
+{
+ int flags = t->signal->flags;
+
+ if (unlikely(flags & SIGNAL_UNKILLABLE) && !from_ancestor_ns)
+ return 1;
+
+ return 0;
+}
+
+static int sig_task_ignored(struct task_struct *t, int sig, int
from_ancestor_ns)
{
void __user *handler;
handler = sig_handler(t, sig);
- if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) &&
+ if (sig_task_unkillable(t, from_ancestor_ns) &&
(handler == SIG_IGN || handler == SIG_DFL))
return 1;
-
+
return sig_handler_ignored(handler, sig);
}
-static int sig_ignored(struct task_struct *t, int sig)
+static int sig_ignored(struct task_struct *t, int sig, int from_ancestor_ns)
{
/*
* Blocked signals are never ignored, since the
@@ -76,7 +90,7 @@ static int sig_ignored(struct task_struct *t, int sig)
if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
return 0;
- if (!sig_task_ignored(t, sig))
+ if (!sig_task_ignored(t, sig, from_ancestor_ns))
return 0;
/*
@@ -632,7 +646,7 @@ static int check_kill_permission(int sig, struct siginfo
*info,
* Returns true if the signal should be actually delivered, otherwise
* it should be dropped.
*/
-static int prepare_signal(int sig, struct task_struct *p)
+static int prepare_signal(int sig, struct task_struct *p, int from_ancestor_ns)
{
struct signal_struct *signal = p->signal;
struct task_struct *t;
@@ -716,7 +730,7 @@ static int prepare_signal(int sig, struct task_struct *p)
}
}
- return !sig_ignored(p, sig);
+ return !sig_ignored(p, sig, from_ancestor_ns);
}
/*
@@ -876,11 +890,15 @@ static int send_signal(int sig, struct siginfo *info,
struct task_struct *t,
{
struct sigpending *pending;
struct sigqueue *q;
+ int from_ancestor_ns;
trace_sched_signal_send(sig, t);
assert_spin_locked(&t->sighand->siglock);
- if (!prepare_signal(sig, t))
+
+ from_ancestor_ns = siginfo_from_ancestor_ns(t, info);
+
+ if (!prepare_signal(sig, t, from_ancestor_ns))
return 0;
pending = group ? &t->signal->shared_pending : &t->pending;
@@ -1375,7 +1393,7 @@ int send_sigqueue(struct sigqueue *q, struct task_struct
*t, int group)
goto ret;
ret = 1; /* the signal is ignored */
- if (!prepare_signal(sig, t))
+ if (!prepare_signal(sig, t, 1))
goto out;
ret = 0;
--
1.5.2.5
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