Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933014Ab0BDAbM (ORCPT ); Wed, 3 Feb 2010 19:31:12 -0500 Received: from e38.co.us.ibm.com ([32.97.110.159]:38241 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932096Ab0BDAbE (ORCPT ); Wed, 3 Feb 2010 19:31:04 -0500 Date: Wed, 3 Feb 2010 18:30:52 -0600 From: "Serge E. Hallyn" To: Kees Cook Cc: James Morris , Casey Schaufler , linux-security-module@vger.kernel.org, Eric Paris , David Howells , Alexey Dobriyan , Ingo Molnar , Andrew Morton , Simon Kagstrom , David Woodhouse , Robin Getz , Greg Kroah-Hartman , Paul Moore , Tetsuo Handa , Stephen Smalley , Etienne Basset , "David P. Quigley" , LKLM Subject: Re: [PATCH v2 1/2] syslog: distinguish between /proc/kmsg and syscalls Message-ID: <20100204003052.GA16681@us.ibm.com> References: <20100202055354.GV19355@outflux.net> <4B67C2EA.705@schaufler-ca.com> <20100202202054.GW19355@outflux.net> <20100202212510.GG32305@us.ibm.com> <20100203233643.GI19355@outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100203233643.GI19355@outflux.net> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10326 Lines: 301 Quoting Kees Cook (kees.cook@canonical.com): > This allows the LSM to distinguish between syslog functions originating > from /proc/kmsg access and direct syscalls. By default, the commoncaps > will now no longer require CAP_SYS_ADMIN to read an opened /proc/kmsg > file descriptor. For example the kernel syslog reader can now drop > privileges after opening /proc/kmsg, instead of staying privileged with > CAP_SYS_ADMIN. MAC systems that implement security_syslog have unchanged > behavior. > > Signed-off-by: Kees Cook Acked-by: Serge Hallyn > --- > fs/proc/kmsg.c | 14 +++++++------- > include/linux/security.h | 11 ++++++----- > include/linux/syslog.h | 29 +++++++++++++++++++++++++++++ > kernel/printk.c | 7 ++++--- > security/commoncap.c | 7 ++++++- > security/security.c | 4 ++-- > security/selinux/hooks.c | 5 +++-- > security/smack/smack_lsm.c | 4 ++-- > 8 files changed, 59 insertions(+), 22 deletions(-) > create mode 100644 include/linux/syslog.h > > diff --git a/fs/proc/kmsg.c b/fs/proc/kmsg.c > index 7ca7834..6a3d843 100644 > --- a/fs/proc/kmsg.c > +++ b/fs/proc/kmsg.c > @@ -12,37 +12,37 @@ > #include > #include > #include > +#include > > #include > #include > > extern wait_queue_head_t log_wait; > > -extern int do_syslog(int type, char __user *bug, int count); > - > static int kmsg_open(struct inode * inode, struct file * file) > { > - return do_syslog(1,NULL,0); > + return do_syslog(1, NULL, 0, SYSLOG_FROM_FILE); > } > > static int kmsg_release(struct inode * inode, struct file * file) > { > - (void) do_syslog(0,NULL,0); > + (void) do_syslog(0, NULL, 0, SYSLOG_FROM_FILE); > return 0; > } > > static ssize_t kmsg_read(struct file *file, char __user *buf, > size_t count, loff_t *ppos) > { > - if ((file->f_flags & O_NONBLOCK) && !do_syslog(9, NULL, 0)) > + if ((file->f_flags & O_NONBLOCK) && > + !do_syslog(9, NULL, 0, SYSLOG_FROM_FILE)) > return -EAGAIN; > - return do_syslog(2, buf, count); > + return do_syslog(2, buf, count, SYSLOG_FROM_FILE); > } > > static unsigned int kmsg_poll(struct file *file, poll_table *wait) > { > poll_wait(file, &log_wait, wait); > - if (do_syslog(9, NULL, 0)) > + if (do_syslog(9, NULL, 0, SYSLOG_FROM_FILE)) > return POLLIN | POLLRDNORM; > return 0; > } > diff --git a/include/linux/security.h b/include/linux/security.h > index 2c627d3..106786e 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -76,7 +76,7 @@ extern int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, > 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); > -extern int cap_syslog(int type); > +extern int cap_syslog(int type, bool from_file); > extern int cap_vm_enough_memory(struct mm_struct *mm, long pages); > > struct msghdr; > @@ -1348,6 +1348,7 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts) > * logging to the console. > * See the syslog(2) manual page for an explanation of the @type values. > * @type contains the type of action. > + * @from_file indicates the context of action (if it came from /proc). > * Return 0 if permission is granted. > * @settime: > * Check permission to change the system time. > @@ -1462,7 +1463,7 @@ struct security_operations { > int (*sysctl) (struct ctl_table *table, int op); > int (*quotactl) (int cmds, int type, int id, struct super_block *sb); > int (*quota_on) (struct dentry *dentry); > - int (*syslog) (int type); > + int (*syslog) (int type, bool from_file); > int (*settime) (struct timespec *ts, struct timezone *tz); > int (*vm_enough_memory) (struct mm_struct *mm, long pages); > > @@ -1761,7 +1762,7 @@ int security_acct(struct file *file); > int security_sysctl(struct ctl_table *table, int op); > int security_quotactl(int cmds, int type, int id, struct super_block *sb); > int security_quota_on(struct dentry *dentry); > -int security_syslog(int type); > +int security_syslog(int type, bool from_file); > int security_settime(struct timespec *ts, struct timezone *tz); > int security_vm_enough_memory(long pages); > int security_vm_enough_memory_mm(struct mm_struct *mm, long pages); > @@ -2007,9 +2008,9 @@ static inline int security_quota_on(struct dentry *dentry) > return 0; > } > > -static inline int security_syslog(int type) > +static inline int security_syslog(int type, bool from_file) > { > - return cap_syslog(type); > + return cap_syslog(type, from_file); > } > > static inline int security_settime(struct timespec *ts, struct timezone *tz) > diff --git a/include/linux/syslog.h b/include/linux/syslog.h > new file mode 100644 > index 0000000..5f02b18 > --- /dev/null > +++ b/include/linux/syslog.h > @@ -0,0 +1,29 @@ > +/* Syslog internals > + * > + * Copyright 2010 Canonical, Ltd. > + * Author: Kees Cook > + * > + * This program is free software; you can redistribute it and/or modify > + * it under the terms of the GNU General Public License as published by > + * the Free Software Foundation; either version 2, or (at your option) > + * any later version. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + * You should have received a copy of the GNU General Public License > + * along with this program; see the file COPYING. If not, write to > + * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. > + */ > + > +#ifndef _LINUX_SYSLOG_H > +#define _LINUX_SYSLOG_H > + > +#define SYSLOG_FROM_CALL 0 > +#define SYSLOG_FROM_FILE 1 > + > +int do_syslog(int type, char __user *buf, int count, bool from_file); > + > +#endif /* _LINUX_SYSLOG_H */ > diff --git a/kernel/printk.c b/kernel/printk.c > index 1751c45..1771b34 100644 > --- a/kernel/printk.c > +++ b/kernel/printk.c > @@ -35,6 +35,7 @@ > #include > #include > #include > +#include > > #include > > @@ -273,14 +274,14 @@ static inline void boot_delay_msec(void) > * 9 -- Return number of unread characters in the log buffer > * 10 -- Return size of the log buffer > */ > -int do_syslog(int type, char __user *buf, int len) > +int do_syslog(int type, char __user *buf, int len, bool from_file) > { > unsigned i, j, limit, count; > int do_clear = 0; > char c; > int error = 0; > > - error = security_syslog(type); > + error = security_syslog(type, from_file); > if (error) > return error; > > @@ -417,7 +418,7 @@ out: > > SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len) > { > - return do_syslog(type, buf, len); > + return do_syslog(type, buf, len, SYSLOG_FROM_CALL); > } > > /* > diff --git a/security/commoncap.c b/security/commoncap.c > index f800fdb..677fad9 100644 > --- a/security/commoncap.c > +++ b/security/commoncap.c > @@ -27,6 +27,7 @@ > #include > #include > #include > +#include > > /* > * If a non-root user executes a setuid-root binary in > @@ -888,12 +889,16 @@ error: > /** > * cap_syslog - Determine whether syslog function is permitted > * @type: Function requested > + * @from_file: Whether this request came from an open file (i.e. /proc) > * > * Determine whether the current process is permitted to use a particular > * syslog function, returning 0 if permission is granted, -ve if not. > */ > -int cap_syslog(int type) > +int cap_syslog(int type, bool from_file) > { > + /* /proc/kmsg can open be opened by CAP_SYS_ADMIN */ > + if (type != 1 && from_file) > + return 0; > if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN)) > return -EPERM; > return 0; > diff --git a/security/security.c b/security/security.c > index 24e060b..9a127ae 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -203,9 +203,9 @@ int security_quota_on(struct dentry *dentry) > return security_ops->quota_on(dentry); > } > > -int security_syslog(int type) > +int security_syslog(int type, bool from_file) > { > - return security_ops->syslog(type); > + return security_ops->syslog(type, from_file); > } > > int security_settime(struct timespec *ts, struct timezone *tz) > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > index 9a2ee84..a4862a0 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -76,6 +76,7 @@ > #include > #include > #include > +#include > > #include "avc.h" > #include "objsec.h" > @@ -2049,11 +2050,11 @@ static int selinux_quota_on(struct dentry *dentry) > return dentry_has_perm(cred, NULL, dentry, FILE__QUOTAON); > } > > -static int selinux_syslog(int type) > +static int selinux_syslog(int type, bool from_file) > { > int rc; > > - rc = cap_syslog(type); > + rc = cap_syslog(type, from_file); > if (rc) > return rc; > > diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c > index 529c9ca..a5721b3 100644 > --- a/security/smack/smack_lsm.c > +++ b/security/smack/smack_lsm.c > @@ -157,12 +157,12 @@ static int smack_ptrace_traceme(struct task_struct *ptp) > * > * Returns 0 on success, error code otherwise. > */ > -static int smack_syslog(int type) > +static int smack_syslog(int type, bool from_file) > { > int rc; > char *sp = current_security(); > > - rc = cap_syslog(type); > + rc = cap_syslog(type, from_file); > if (rc != 0) > return rc; > > -- > 1.6.5 > > > -- > Kees Cook > Ubuntu Security Team -- 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/