Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937133AbYCSV0N (ORCPT ); Wed, 19 Mar 2008 17:26:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762062AbYCSUA6 (ORCPT ); Wed, 19 Mar 2008 16:00:58 -0400 Received: from over.ny.us.ibm.com ([32.97.182.150]:33535 "EHLO over.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753195AbYCSUA5 (ORCPT ); Wed, 19 Mar 2008 16:00:57 -0400 Date: Wed, 19 Mar 2008 11:56:35 -0500 From: "Serge E. Hallyn" To: lkml , Linus Torvalds Cc: Andrew Morton , Andrew Morgan , buraphalinuxserver@gmail.com, "Luiz Fernando N. Capitulino" Subject: [PATCH 1/1] file capabilities: remove cap_task_kill() (-git) Message-ID: <20080319165635.GH5935@sergelap.ibm.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: 4565 Lines: 129 (resending once against -git. I had sent against -stable in http://lkml.org/lkml/2008/2/28/225. Without this patch, atd is broken at least on some distros.) 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(). One example of a still-broken application is 'at' for non-root users. This patch removes cap_task_kill(). Signed-off-by: Serge Hallyn Acked-by: Andrew G. Morgan --- include/linux/security.h | 3 +-- security/capability.c | 1 - security/commoncap.c | 40 ---------------------------------------- 3 files changed, 1 insertions(+), 43 deletions(-) diff --git a/include/linux/security.h b/include/linux/security.h index b07357c..c673dfd 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -57,7 +57,6 @@ 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); @@ -2187,7 +2186,7 @@ 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) -- 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/