Commit 18d872f7 authored Apr 04, 2016 by Rafal Krypa Committed by Casey Schaufler Jun 08, 2016

Smack: ignore null signal in smack_task_kill



Kill with signal number 0 is commonly used for checking PID existence.
Smack treated such cases like any other kills, although no signal is
actually delivered when sig == 0.

Checking permissions when sig == 0 didn't prevent an unprivileged caller
from learning whether PID exists or not. When it existed, kernel returned
EPERM, when it didn't - ESRCH. The only effect of policy check in such
case is noise in audit logs.

This change lets Smack silently ignore kill() invocations with sig == 0.

Signed-off-by: Rafal Krypa <r.krypa@samsung.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>

parent 40d27378

security/smack/smack_lsm.c

+3 −0

Original line number	Original line	Diff line number	Diff line
	@@ -2227,6 +2227,9 @@ static int smack_task_kill(struct task_struct p, struct siginfo info,
	struct smack_known *tkp = smk_of_task_struct(p);		struct smack_known *tkp = smk_of_task_struct(p);
	int rc;		int rc;

			if (!sig)
			return 0; /* null signal; existence test */

	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);		smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
	smk_ad_setfield_u_tsk(&ad, p);		smk_ad_setfield_u_tsk(&ad, p);
	/*		/*