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Subject[PATCH 7/7][v7] proc: Show SIG_DFL signals to init as "ignored" signals

From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Date: Sat, 17 Jan 2009 09:26:26 -0800
Subject: [PATCH 7/7][v7] proc: Show SIG_DFL signals to init as "ignored" signals

Init processes ignore SIG_DFL signals unless they are from an ancestor
namespace. Ensure /proc/pid/status correcly reports these signals.

Values for "normal" /bin/bash from /proc/pid/status:

SigIgn: 0000000000384004
SigCgt: 000000004b813efb
Signals 9, 16, 19 etc are neither ignored nor caught

/bin/bash as container-init, Status viewed from outside container:

SigIgn: 0000000000384004
SigCgt: 000000004b813efb
(same as 'normal')

/bin/bash as container-init, Status viewed from inside container:

SigIgn: ffffffffb47ec104
SigCgt: 000000004b813efb
All "uncaught" signals, including SIGKILL(9) SIGSTOP(19) are ignored.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
---
fs/proc/array.c | 18 +++++++++++++++++-
1 files changed, 17 insertions(+), 1 deletions(-)
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 7e4877d..16e39db 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -228,15 +228,31 @@ static void render_sigset_t(struct seq_file *m, const char *header,
seq_printf(m, "\n");
}

+static int is_unkillable(struct task_struct *p)
+{
+ if (!(p->signal->flags & SIGNAL_UNKILLABLE))
+ return 0;
+
+ /* If caller is an ancestor, we are not unkillable */
+ if (task_pid_nr_ns(current, task_active_pid_ns(p)) <= 0)
+ return 0;
+
+ return 1;
+}
+
static void collect_sigign_sigcatch(struct task_struct *p, sigset_t *ign,
sigset_t *catch)
{
struct k_sigaction *k;
int i;
+ int unkillable;
+
+ unkillable = is_unkillable(p);

k = p->sighand->action;
for (i = 1; i <= _NSIG; ++i, ++k) {
- if (k->sa.sa_handler == SIG_IGN)
+ if (k->sa.sa_handler == SIG_IGN ||
+ (k->sa.sa_handler == SIG_DFL && unkillable))
sigaddset(ign, i);
else if (k->sa.sa_handler != SIG_DFL)
sigaddset(catch, i);
--
1.5.2.5


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