Smack: Signal delivery as an append operation

Under a strict subject/object security policy delivering a
signal or delivering network IPC could be considered either
a write or an append operation. The original choice to make
both write operations leads to an issue where IPC delivery
is desired under policy, but delivery of signals is not.
This patch provides the option of making signal delivery
an append operation, allowing Smack rules that deny signal
delivery while allowing IPC. This was requested for Tizen.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/security/smack/Kconfig b/security/smack/Kconfig
index 271adae81796..923b120e0fa5 100644
--- a/security/smack/Kconfig
+++ b/security/smack/Kconfig
@@ -40,3 +40,15 @@ config SECURITY_SMACK_NETFILTER
 	  This enables security marking of network packets using
 	  Smack labels.
 	  If you are unsure how to answer this question, answer N.
+
+config SECURITY_SMACK_APPEND_SIGNALS
+	bool "Treat delivering signals as an append operation"
+	depends on SECURITY_SMACK
+	default n
+	help
+	  Sending a signal has been treated as a write operation to the
+	  receiving process. If this option is selected, the delivery
+	  will be an append operation instead. This makes it possible
+	  to differentiate between delivering a network packet and
+	  delivering a signal in the Smack rules.
+	  If you are unsure how to answer this question, answer N.