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authorCasey Schaufler <casey@schaufler-ca.com>2016-08-30 10:31:39 -0700
committerCasey Schaufler <casey@schaufler-ca.com>2016-09-08 13:22:56 -0700
commitc60b906673eebb4f65840fa9dc204401caf276ea (patch)
tree0ccaf8637751e3183918c3249af3ab465481245f
parent63e24c497158c066583b9c06378d89ace694265a (diff)
downloadlinux-c60b906673eebb4f65840fa9dc204401caf276ea.tar.gz
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>
-rw-r--r--security/smack/Kconfig12
-rw-r--r--security/smack/smack.h10
-rw-r--r--security/smack/smack_lsm.c14
3 files changed, 29 insertions, 7 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.
diff --git a/security/smack/smack.h b/security/smack/smack.h
index 26e58f1804b1..51fd30192c08 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -256,6 +256,16 @@ enum {
#define MAY_LOCK 0x00002000 /* Locks should be writes, but ... */
#define MAY_BRINGUP 0x00004000 /* Report use of this rule */
+/*
+ * The policy for delivering signals is configurable.
+ * It is usually "write", but can be "append".
+ */
+#ifdef CONFIG_SECURITY_SMACK_APPEND_SIGNALS
+#define MAY_DELIVER MAY_APPEND /* Signal delivery requires append */
+#else
+#define MAY_DELIVER MAY_WRITE /* Signal delivery requires write */
+#endif
+
#define SMACK_BRINGUP_ALLOW 1 /* Allow bringup mode */
#define SMACK_UNCONFINED_SUBJECT 2 /* Allow unconfined label */
#define SMACK_UNCONFINED_OBJECT 3 /* Allow unconfined label */
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 87a9741b0d02..caec2256ab22 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1857,14 +1857,14 @@ static int smack_file_send_sigiotask(struct task_struct *tsk,
/* we don't log here as rc can be overriden */
skp = file->f_security;
- rc = smk_access(skp, tkp, MAY_WRITE, NULL);
- rc = smk_bu_note("sigiotask", skp, tkp, MAY_WRITE, rc);
+ rc = smk_access(skp, tkp, MAY_DELIVER, NULL);
+ rc = smk_bu_note("sigiotask", skp, tkp, MAY_DELIVER, rc);
if (rc != 0 && has_capability(tsk, CAP_MAC_OVERRIDE))
rc = 0;
smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
smk_ad_setfield_u_tsk(&ad, tsk);
- smack_log(skp->smk_known, tkp->smk_known, MAY_WRITE, rc, &ad);
+ smack_log(skp->smk_known, tkp->smk_known, MAY_DELIVER, rc, &ad);
return rc;
}
@@ -2265,8 +2265,8 @@ static int smack_task_kill(struct task_struct *p, struct siginfo *info,
* can write the receiver.
*/
if (secid == 0) {
- rc = smk_curacc(tkp, MAY_WRITE, &ad);
- rc = smk_bu_task(p, MAY_WRITE, rc);
+ rc = smk_curacc(tkp, MAY_DELIVER, &ad);
+ rc = smk_bu_task(p, MAY_DELIVER, rc);
return rc;
}
/*
@@ -2275,8 +2275,8 @@ static int smack_task_kill(struct task_struct *p, struct siginfo *info,
* we can't take privilege into account.
*/
skp = smack_from_secid(secid);
- rc = smk_access(skp, tkp, MAY_WRITE, &ad);
- rc = smk_bu_note("USB signal", skp, tkp, MAY_WRITE, rc);
+ rc = smk_access(skp, tkp, MAY_DELIVER, &ad);
+ rc = smk_bu_note("USB signal", skp, tkp, MAY_DELIVER, rc);
return rc;
}