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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>
This commit is contained in:
Oleg Nesterov 2008-04-30 00:52:42 -07:00 committed by Linus Torvalds
parent 9e3bd6c3fb
commit 3b5e9e53c6
3 changed files with 14 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

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);
}

3
security/selinux/hooks.c
View File

@ -3286,9 +3286,6 @@ static int selinux_task_kill(struct task_struct *p, struct siginfo *info,
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

9
security/smack/smack_lsm.c
View File

@ -1130,15 +1130,6 @@ static int smack_task_movememory(struct task_struct *p)
static int smack_task_kill(struct task_struct *p, struct siginfo *info,
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.