On 4/4/2016 2:14 AM, Rafal Krypa wrote: > 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.kr...@samsung.com>
Acked-by: Casey Schaufler <ca...@schaufler-ca.com> Applied to git://github.com/cschaufler/smack-next.git#smack-for-4.8 > --- > security/smack/smack_lsm.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c > index 11f7901..3d9bbed 100644 > --- a/security/smack/smack_lsm.c > +++ b/security/smack/smack_lsm.c > @@ -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); > int rc; > > + if (!sig) > + return 0; /* null signal; existence test */ > + > smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK); > smk_ad_setfield_u_tsk(&ad, p); > /*
