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Subject[PATCH 4/7][v6] Define siginfo_from_ancestor_ns()

From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Date: Wed, 24 Dec 2008 13:46:02 -0800
Subject: [PATCH 4/7][v6] Define siginfo_from_ancestor_ns()

Determine if sender of a signal is from an ancestor namespace. This
function will be used in a follow-on patch.

This is based on discussions on the patch from Oleg Nesterov and me
http://lkml.org/lkml/2008/11/25/462.

Changelog[v6]:
- (Oleg Nesterov) Simplify/correct comments
- (Oleg Nesterov) Remove 'ns == NULL' check since task_active_pid_ns()
will return a valid ns for the target.
- (Roland Mcgrath) Remove incorrect SI_ASYNCIO check in
siginfo_from_user().
Changelog[v5]:
- (Oleg Nesterov) Put siginfo_from_ancestor_ns() back under
CONFIG_PID_NS.
- (Oleg Nesterov) Remove the warning in rt_sigqueueinfo().

Changelog[v4]:
- siginfo_from_ancestor_ns() is fairly clean and it does not need
to be under CONFIG_PID_NS. Only siginfo_from_user() needs to be.
- Warn if rt_sigqueueinfo() uses SI_ASYNCIO.
- Added a check for pid-ns of receiver being NULL (in case it is
exiting).

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
---
kernel/signal.c | 37 +++++++++++++++++++++++++++++++++++++
1 files changed, 37 insertions(+), 0 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index bb3b6f5..d0dfa0d 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -820,6 +820,43 @@ static inline int legacy_queue(struct sigpending *signals, int sig)
{
return (sig < SIGRTMIN) && sigismember(&signals->signal, sig);
}
+/*
+ * Return 1 if this signal originated directly from a user process (i.e via
+ * kill(), tkill(), sigqueue()). Return 0 otherwise.
+ */
+#ifdef CONFIG_PID_NS
+static inline int siginfo_from_user(siginfo_t *info)
+{
+ if (!is_si_special(info) && SI_FROMUSER(info))
+ return 1;
+
+ return 0;
+}
+
+static inline int siginfo_from_ancestor_ns(struct task_struct *t,
+ siginfo_t *info)
+{
+ /*
+ * If we do not have a pid in the receiver's namespace,
+ * we must be from an ancestor namespace.
+ */
+ if (siginfo_from_user(info) &&
+ task_pid_nr_ns(current, task_active_pid_ns(t)) <= 0) {
+ return 1;
+ }
+
+ return 0;
+}
+
+#else
+
+static inline int siginfo_from_ancestor_ns(struct task_struct *t,
+ siginfo_t *info)
+{
+ return 0;
+}
+
+#endif

static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
int group, int from_ancestor_ns)
--
1.5.2.5


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