signals: cleanup security_task_kill() usage/implementation
Every implementation of ->task_kill() does nothing when the signal comes from
the kernel. This is correct, but means that check_kill_permission() should
call security_task_kill() only for SI_FROMUSER() case, and we can remove the
same check from ->task_kill() implementations.
(sadly, check_kill_permission() is the last user of signal->session/__session
but we can't s/task_session_nr/task_session/ here).
NOTE: Eric W. Biederman pointed out cap_task_kill() should die, and I think
he is very right.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Cc: David Quigley <dpquigl@tycho.nsa.gov>
Cc: Eric Paris <eparis@redhat.com>
Cc: Harald Welte <laforge@gnumonks.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/signal.c b/kernel/signal.c
index f9a52c7..91d57f8 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -533,22 +533,23 @@
static int check_kill_permission(int sig, struct siginfo *info,
struct task_struct *t)
{
- int error = -EINVAL;
+ int error;
+
if (!valid_signal(sig))
+ return -EINVAL;
+
+ if (info != SEND_SIG_NOINFO && (is_si_special(info) || SI_FROMKERNEL(info)))
+ return 0;
+
+ error = audit_signal_info(sig, t); /* Let audit system see the signal */
+ if (error)
return error;
- if (info == SEND_SIG_NOINFO || (!is_si_special(info) && SI_FROMUSER(info))) {
- error = audit_signal_info(sig, t); /* Let audit system see the signal */
- if (error)
- return error;
- error = -EPERM;
- if (((sig != SIGCONT) ||
- (task_session_nr(current) != task_session_nr(t)))
- && (current->euid ^ t->suid) && (current->euid ^ t->uid)
- && (current->uid ^ t->suid) && (current->uid ^ t->uid)
- && !capable(CAP_KILL))
- return error;
- }
+ if (((sig != SIGCONT) || (task_session_nr(current) != task_session_nr(t)))
+ && (current->euid ^ t->suid) && (current->euid ^ t->uid)
+ && (current->uid ^ t->suid) && (current->uid ^ t->uid)
+ && !capable(CAP_KILL))
+ return -EPERM;
return security_task_kill(t, info, sig, 0);
}
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 85a2204..1b50a6e 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3286,9 +3286,6 @@
if (rc)
return rc;
- if (info != SEND_SIG_NOINFO && (is_si_special(info) || SI_FROMKERNEL(info)))
- return 0;
-
if (!sig)
perm = PROCESS__SIGNULL; /* null signal; existence test */
else
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index fe0ae1b..b5c8f92 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1131,15 +1131,6 @@
int sig, u32 secid)
{
/*
- * Special cases where signals really ought to go through
- * in spite of policy. Stephen Smalley suggests it may
- * make sense to change the caller so that it doesn't
- * bother with the LSM hook in these cases.
- */
- if (info != SEND_SIG_NOINFO &&
- (is_si_special(info) || SI_FROMKERNEL(info)))
- return 0;
- /*
* Sending a signal requires that the sender
* can write the receiver.
*/