On Fri, 2007-09-14 at 09:27 +0900, Yuichi Nakamura wrote:
> Hello.
>
> I would like to propose patch that reduces overhead in read/write by SELinux.
> I sent RFC in previous thread.
> http://lkml.org/lkml/2007/9/6/14
> As a result of discussion in previous thread,
> quality of code has improved, so I would like to submit patch here.
>
> 1. Background
> Look at benchmark result below.
> lmbench simple read/write(average of 5 run).
> Big overhead exists especially on SH(SuperH) arch.
>
> 1) Result for x86(Pentium 4 2.6Ghz), kernel 2.6.22
> Base SELinux Overhead(%)
> Simple read 1.10 1.24 12.3
> Simple write 1.02 1.14 14.0
> * Base: kernel compiled without SELinux support
>
> 2) Result for SH(SH4, SH7751R), kernel 2.6.22
> Base SELinux Overhead(%)
> Simple read 2.39 5.49 130.5
> Simple write 2.07 5.10 146.6
>
> 2. About patch
> It reduces the selinux overhead on read/write by only revalidating
> permissions in selinux_file_permission if the task or inode labels have
> changed or the policy has changed since the open-time check.
> A new LSM hook, security_dentry_open, is added to capture
> the necessary state at open time to allow this optimization.
>
> 3. Result of benchmark after applying patch
> 1) Result for x86(Pentium 4 2.6Ghz), kernel 2.6.22
> Base SELinux Overhead(%)
> Simple read 1.10 1.13 2.3(Before 12.3)
> Simple write 1.02 1.024 0.6(Before 14.0)
> * Base: kernel compiled without SELinux support
>
> 2) Result for SH(SH4, SH7751R), kernel 2.6.22
> Base SELinux Overhead(%)
> Simple read 2.39 2.63 10.4(Before 130.5)
> Simple write 2.07 2.34 13.1(Before 146.6)
>
> Overhead in read/write is reduced a lot.
> This patch adds permission check at open time(in __dentry_open),
> but open/close performance does not get worse as shown below.
>
> * Lmbench simple open/close
> Pentium 4(before patch):
> Base SELinux Overhead(%)
> open/close 5.97 7.45 24.9
> after patch:
> open/close 5.97 7.48 25.3
>
> SH(before patch):
> Base SELinux Overhead(%)
> open/close 32.6 62.8 93.0
> after patch:
> open/close 32.6 58.7 80.2
>
> Next is a patch for 2.6.22.
>
> It reduces the selinux overhead on read/write by only revalidating
> permissions in selinux_file_permission if the task or inode labels have
> changed or the policy has changed since the open-time check. A new LSM
> hook, security_dentry_open, is added to capture the necessary state at
> open time to allow this optimization.
>
> Signed-off-by: Yuichi Nakamura<[email protected]>
Thanks, looks good.
Acked-by: Stephen Smalley <[email protected]>
> ---
> fs/open.c | 4 ++
> include/linux/security.h | 18 ++++++++++++
> security/dummy.c | 6 ++++
> security/selinux/avc.c | 5 +++
> security/selinux/hooks.c | 53 +++++++++++++++++++++++++++++++++++++-
> security/selinux/include/avc.h | 2 +
> security/selinux/include/objsec.h | 2 +
> 7 files changed, 89 insertions(+), 1 deletion(-)
> diff -purN -X linux-2.6.22/Documentation/dontdiff linux-2.6.22.orig/security/selinux/avc.c linux-2.6.22/security/selinux/avc.c
> --- linux-2.6.22.orig/security/selinux/avc.c 2007-07-09 08:32:17.000000000 +0900
> +++ linux-2.6.22/security/selinux/avc.c 2007-09-14 08:35:04.000000000 +0900
> @@ -913,3 +913,8 @@ int avc_has_perm(u32 ssid, u32 tsid, u16
> avc_audit(ssid, tsid, tclass, requested, &avd, rc, auditdata);
> return rc;
> }
> +
> +u32 avc_policy_seqno(void)
> +{
> + return avc_cache.latest_notif;
> +}
> diff -purN -X linux-2.6.22/Documentation/dontdiff linux-2.6.22.orig/security/selinux/hooks.c linux-2.6.22/security/selinux/hooks.c
> --- linux-2.6.22.orig/security/selinux/hooks.c 2007-07-09 08:32:17.000000000 +0900
> +++ linux-2.6.22/security/selinux/hooks.c 2007-09-14 08:43:51.000000000 +0900
> @@ -14,6 +14,8 @@
> * <[email protected]>
> * Copyright (C) 2006 Hewlett-Packard Development Company, L.P.
> * Paul Moore, <[email protected]>
> + * Copyright (C) 2007 Hitachi Software Engineering Co., Ltd.
> + * Yuichi Nakamura <[email protected]>
> *
> * This program is free software; you can redistribute it and/or modify
> * it under the terms of the GNU General Public License version 2,
> @@ -2458,7 +2460,7 @@ static int selinux_inode_listsecurity(st
>
> /* file security operations */
>
> -static int selinux_file_permission(struct file *file, int mask)
> +static int selinux_revalidate_file_permission(struct file *file, int mask)
> {
> int rc;
> struct inode *inode = file->f_path.dentry->d_inode;
> @@ -2480,6 +2482,25 @@ static int selinux_file_permission(struc
> return selinux_netlbl_inode_permission(inode, mask);
> }
>
> +static int selinux_file_permission(struct file *file, int mask)
> +{
> + struct inode *inode = file->f_path.dentry->d_inode;
> + struct task_security_struct *tsec = current->security;
> + struct file_security_struct *fsec = file->f_security;
> + struct inode_security_struct *isec = inode->i_security;
> +
> + if (!mask) {
> + /* No permission to check. Existence test. */
> + return 0;
> + }
> +
> + if (tsec->sid == fsec->sid && fsec->isid == isec->sid
> + && fsec->pseqno == avc_policy_seqno())
> + return selinux_netlbl_inode_permission(inode, mask);
> +
> + return selinux_revalidate_file_permission(file, mask);
> +}
> +
> static int selinux_file_alloc_security(struct file *file)
> {
> return file_alloc_security(file);
> @@ -2715,6 +2736,34 @@ static int selinux_file_receive(struct f
> return file_has_perm(current, file, file_to_av(file));
> }
>
> +static int selinux_dentry_open(struct file *file)
> +{
> + struct file_security_struct *fsec;
> + struct inode *inode;
> + struct inode_security_struct *isec;
> + inode = file->f_path.dentry->d_inode;
> + fsec = file->f_security;
> + isec = inode->i_security;
> + /*
> + * Save inode label and policy sequence number
> + * at open-time so that selinux_file_permission
> + * can determine whether revalidation is necessary.
> + * Task label is already saved in the file security
> + * struct as its SID.
> + */
> + fsec->isid = isec->sid;
> + fsec->pseqno = avc_policy_seqno();
> + /*
> + * Since the inode label or policy seqno may have changed
> + * between the selinux_inode_permission check and the saving
> + * of state above, recheck that access is still permitted.
> + * Otherwise, access might never be revalidated against the
> + * new inode label or new policy.
> + * This check is not redundant - do not remove.
> + */
> + return inode_has_perm(current, inode, file_to_av(file), NULL);
> +}
> +
> /* task security operations */
>
> static int selinux_task_create(unsigned long clone_flags)
> @@ -4780,6 +4829,8 @@ static struct security_operations selinu
> .file_send_sigiotask = selinux_file_send_sigiotask,
> .file_receive = selinux_file_receive,
>
> + .dentry_open = selinux_dentry_open,
> +
> .task_create = selinux_task_create,
> .task_alloc_security = selinux_task_alloc_security,
> .task_free_security = selinux_task_free_security,
> diff -purN -X linux-2.6.22/Documentation/dontdiff linux-2.6.22.orig/security/selinux/include/avc.h linux-2.6.22/security/selinux/include/avc.h
> --- linux-2.6.22.orig/security/selinux/include/avc.h 2007-07-09 08:32:17.000000000 +0900
> +++ linux-2.6.22/security/selinux/include/avc.h 2007-09-14 08:35:04.000000000 +0900
> @@ -110,6 +110,8 @@ int avc_has_perm(u32 ssid, u32 tsid,
> u16 tclass, u32 requested,
> struct avc_audit_data *auditdata);
>
> +u32 avc_policy_seqno(void);
> +
> #define AVC_CALLBACK_GRANT 1
> #define AVC_CALLBACK_TRY_REVOKE 2
> #define AVC_CALLBACK_REVOKE 4
> diff -purN -X linux-2.6.22/Documentation/dontdiff linux-2.6.22.orig/security/selinux/include/objsec.h linux-2.6.22/security/selinux/include/objsec.h
> --- linux-2.6.22.orig/security/selinux/include/objsec.h 2007-07-09 08:32:17.000000000 +0900
> +++ linux-2.6.22/security/selinux/include/objsec.h 2007-09-14 08:35:04.000000000 +0900
> @@ -53,6 +53,8 @@ struct file_security_struct {
> struct file *file; /* back pointer to file object */
> u32 sid; /* SID of open file description */
> u32 fown_sid; /* SID of file owner (for SIGIO) */
> + u32 isid; /* SID of inode at the time of file open */
> + u32 pseqno; /* Policy seqno at the time of file open */
> };
>
> struct superblock_security_struct {
> diff -purN -X linux-2.6.22/Documentation/dontdiff linux-2.6.22.orig/fs/open.c linux-2.6.22/fs/open.c
> --- linux-2.6.22.orig/fs/open.c 2007-07-09 08:32:17.000000000 +0900
> +++ linux-2.6.22/fs/open.c 2007-09-14 08:40:46.000000000 +0900
> @@ -696,6 +696,10 @@ static struct file *__dentry_open(struct
> f->f_op = fops_get(inode->i_fop);
> file_move(f, &inode->i_sb->s_files);
>
> + error = security_dentry_open(f);
> + if (error)
> + goto cleanup_all;
> +
> if (!open && f->f_op)
> open = f->f_op->open;
> if (open) {
> diff -purN -X linux-2.6.22/Documentation/dontdiff linux-2.6.22.orig/include/linux/security.h linux-2.6.22/include/linux/security.h
> --- linux-2.6.22.orig/include/linux/security.h 2007-07-09 08:32:17.000000000 +0900
> +++ linux-2.6.22/include/linux/security.h 2007-09-14 08:44:13.000000000 +0900
> @@ -503,6 +503,13 @@ struct request_sock;
> * @file contains the file structure being received.
> * Return 0 if permission is granted.
> *
> + * Security hook for dentry
> + *
> + * @dentry_open
> + * Save open-time permission checking state for later use upon
> + * file_permission, and recheck access if anything has changed
> + * since inode_permission.
> + *
> * Security hooks for task operations.
> *
> * @task_create:
> @@ -1253,6 +1260,7 @@ struct security_operations {
> int (*file_send_sigiotask) (struct task_struct * tsk,
> struct fown_struct * fown, int sig);
> int (*file_receive) (struct file * file);
> + int (*dentry_open) (struct file *file);
>
> int (*task_create) (unsigned long clone_flags);
> int (*task_alloc_security) (struct task_struct * p);
> @@ -1854,6 +1862,11 @@ static inline int security_file_receive
> return security_ops->file_receive (file);
> }
>
> +static inline int security_dentry_open (struct file *file)
> +{
> + return security_ops->dentry_open (file);
> +}
> +
> static inline int security_task_create (unsigned long clone_flags)
> {
> return security_ops->task_create (clone_flags);
> @@ -2529,6 +2542,11 @@ static inline int security_file_receive
> return 0;
> }
>
> +static inline int security_dentry_open (struct file *file)
> +{
> + return 0;
> +}
> +
> static inline int security_task_create (unsigned long clone_flags)
> {
> return 0;
> --- linux-2.6.22.orig/security/dummy.c 2007-07-09 08:32:17.000000000 +0900
> +++ linux-2.6.22/security/dummy.c 2007-09-14 08:35:04.000000000 +0900
> @@ -459,6 +459,11 @@ static int dummy_file_receive (struct fi
> return 0;
> }
>
> +static int dummy_dentry_open (struct file *file)
> +{
> + return 0;
> +}
> +
> static int dummy_task_create (unsigned long clone_flags)
> {
> return 0;
> @@ -1029,6 +1034,7 @@ void security_fixup_ops (struct security
> set_to_dummy_if_null(ops, file_set_fowner);
> set_to_dummy_if_null(ops, file_send_sigiotask);
> set_to_dummy_if_null(ops, file_receive);
> + set_to_dummy_if_null(ops, dentry_open);
> set_to_dummy_if_null(ops, task_create);
> set_to_dummy_if_null(ops, task_alloc_security);
> set_to_dummy_if_null(ops, task_free_security);
>
> Regards,
--
Stephen Smalley
National Security Agency
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