Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760981AbYB1RlU (ORCPT ); Thu, 28 Feb 2008 12:41:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754475AbYB1RlI (ORCPT ); Thu, 28 Feb 2008 12:41:08 -0500 Received: from smtp110.sbc.mail.re2.yahoo.com ([68.142.229.95]:27458 "HELO smtp110.sbc.mail.re2.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752083AbYB1RlH (ORCPT ); Thu, 28 Feb 2008 12:41:07 -0500 X-YMail-OSG: Vb6xrHMVM1njHbNtUMN9NJv3AiuMfheKY9T6XV6TCg923Ctslzglz7hV_iioz3SI8rb3r0McTrWu0ix4623jmL7_d6w9CRQGaVQjh52cmLg1OrOX7Q-- X-Yahoo-Newman-Property: ymail-3 Date: Thu, 28 Feb 2008 11:38:17 -0600 From: serge@hallyn.com To: lkml , linux-security-module@vger.kernel.org Cc: Andrew Morgan , Stephen Smalley , Mike Galbraith , buraphalinuxserver@gmail.com, elendil@planet.nl Subject: [PATCH 1/1] file capabilities: remove cap_task_kill() Message-ID: <20080228173817.GA32661@vino.hallyn.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4887 Lines: 139 The original justification for cap_task_kill() was as follows: check_kill_permission() does appropriate uid equivalence checks. However with file capabilities it becomes possible for an unprivileged user to execute a file with file capabilities resulting in a more privileged task with the same uid. However now that cap_task_kill() always returns 0 (permission granted) when p->uid==current->uid, the whole hook is worthless, and only likely to create more subtle problems in the corner cases where it might still be called but return -EPERM. Those cases are basically when uids are different but euid/suid is equivalent as per the check in check_kill_permission(). This patch removes cap_task_kill(). Signed-off-by: Serge Hallyn --- include/linux/security.h | 3 +-- security/capability.c | 1 - security/commoncap.c | 40 ---------------------------------------- security/smack/smack_lsm.c | 5 ----- 4 files changed, 1 insertions(+), 48 deletions(-) diff --git a/include/linux/security.h b/include/linux/security.h index fe52cde..95cb830 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -63,7 +63,6 @@ extern int cap_inode_need_killpriv(struct dentry *dentry); extern int cap_inode_killpriv(struct dentry *dentry); extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, int flags); extern void cap_task_reparent_to_init (struct task_struct *p); -extern int cap_task_kill(struct task_struct *p, struct siginfo *info, int sig, u32 secid); extern int cap_task_setscheduler (struct task_struct *p, int policy, struct sched_param *lp); extern int cap_task_setioprio (struct task_struct *p, int ioprio); extern int cap_task_setnice (struct task_struct *p, int nice); @@ -2138,7 +2137,7 @@ static inline int security_task_kill (struct task_struct *p, struct siginfo *info, int sig, u32 secid) { - return cap_task_kill(p, info, sig, secid); + return 0; } static inline int security_task_wait (struct task_struct *p) diff --git a/security/capability.c b/security/capability.c index 9e99f36..2c6e06d 100644 --- a/security/capability.c +++ b/security/capability.c @@ -40,7 +40,6 @@ static struct security_operations capability_ops = { .inode_need_killpriv = cap_inode_need_killpriv, .inode_killpriv = cap_inode_killpriv, - .task_kill = cap_task_kill, .task_setscheduler = cap_task_setscheduler, .task_setioprio = cap_task_setioprio, .task_setnice = cap_task_setnice, diff --git a/security/commoncap.c b/security/commoncap.c index bb0c095..06d5c94 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -540,41 +540,6 @@ int cap_task_setnice (struct task_struct *p, int nice) return cap_safe_nice(p); } -int cap_task_kill(struct task_struct *p, struct siginfo *info, - int sig, u32 secid) -{ - if (info != SEND_SIG_NOINFO && (is_si_special(info) || SI_FROMKERNEL(info))) - return 0; - - /* - * Running a setuid root program raises your capabilities. - * Killing your own setuid root processes was previously - * allowed. - * We must preserve legacy signal behavior in this case. - */ - if (p->uid == current->uid) - return 0; - - /* sigcont is permitted within same session */ - if (sig == SIGCONT && (task_session_nr(current) == task_session_nr(p))) - return 0; - - if (secid) - /* - * Signal sent as a particular user. - * Capabilities are ignored. May be wrong, but it's the - * only thing we can do at the moment. - * Used only by usb drivers? - */ - return 0; - if (cap_issubset(p->cap_permitted, current->cap_permitted)) - return 0; - if (capable(CAP_KILL)) - return 0; - - return -EPERM; -} - /* * called from kernel/sys.c for prctl(PR_CABSET_DROP) * done without task_capability_lock() because it introduces @@ -605,11 +570,6 @@ int cap_task_setnice (struct task_struct *p, int nice) { return 0; } -int cap_task_kill(struct task_struct *p, struct siginfo *info, - int sig, u32 secid) -{ - return 0; -} #endif void cap_task_reparent_to_init (struct task_struct *p) diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 770eb06..a9ca412 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -1124,11 +1124,6 @@ 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) { - int rc; - - rc = cap_task_kill(p, info, sig, secid); - if (rc != 0) - return rc; /* * Special cases where signals really ought to go through * in spite of policy. Stephen Smalley suggests it may -- 1.5.2.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/