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signals: cleanup security_task_kill() usage/implementation

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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 <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Serge Hallyn <[email protected]>
Cc: Roland McGrath <[email protected]>
Cc: Casey Schaufler <[email protected]>
Cc: David Quigley <[email protected]>
Cc: Eric Paris <[email protected]>
Cc: Harald Welte <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: Stephen Smalley <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Oleg Nesterov 2008-04-30 00:52:42 -07:00 • committed by Linus Torvalds
commit 3b5e9e53c6
3 changed files with 14 additions and 25 deletions
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27
kernel/signal.c
View file

@ -533,22 +533,23 @@ static int rm_from_queue(unsigned long mask, struct sigpending *s)
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);
}