Messages in this thread Patch in this message | | | Date | Thu, 06 Sep 2007 16:27:16 +0900 | From | Yuichi Nakamura <> | Subject | [RFC]selinux: Improving SELinux read/write performance |
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Hello.
As I posted before in selinux list, I found big overhead of SELinux in read/write on some CPUs, and trying tuning. There were discussion in previous threads. Part 1: http://marc.info/?t=118845343400001&r=1&w=2 Part 2: http://marc.info/?t=118880749800004&r=1&w=2
I would like to RFC again about this topic.
1. Background Look at benchmark result below. lmbench simple read/write. 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 1.00 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 # This result is a little different from previous threads, # because I changed some kernel configs.
Overhead more than 100% I also found about 70-90% overhead in ARM.
2. About patch I found a overhead in selinux_file_permission function. This is a function that is called in read/write calls, and does SELinux permission check. SELinux checks permission both in open and read/write time. Stephen Smalley sugessted that we can usually skip permission check in selinux_file_permission. By this patch, permission check in selinux_file_permssion is done only when - sid of task has changed after file open - sid of inode has changed after file open - policy load or boolean change happen after file open
To detect these changes, I added entries in file_security struct and saving these values at file open.
And to save sid of inode at the time of file open, I had to add new LSM hook in __dentry_open function.
3. Benchmark after applying this patch 1) Result for x86(Pentium 4 2.6Ghz), kernel 2.6.22 Base SELinux Overhead(%) Simple read 1.10 1.12 1.6(Before 12.3) Simple write 1.00 1.03 3.6(Before 14.0)
2) Result for SH(SH4, SH7751R), kernel 2.6.22 Base SELinux Overhead(%) Simple read 2.39 2.65 11.1(Before 130.5) Simple write 2.07 2.28 10.5(Before 146.6)
Performance has improved a lot. I want comments from community.
Signed-off-by: Yuichi Nakamura<ynakam@hitachisoft.jp> --- fs/open.c | 5 +++ include/linux/security.h | 11 +++++++ security/selinux/avc.c | 5 ++- security/selinux/hooks.c | 54 +++++++++++++++++++++++++++++++++++++- security/selinux/include/objsec.h | 3 ++ 5 files changed, 76 insertions(+), 2 deletions(-) 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 2007-09-06 14:33:35.000000000 +0900 @@ -123,6 +123,7 @@ DEFINE_PER_CPU(struct avc_cache_stats, a #endif static struct avc_cache avc_cache; +u32 policy_seqno = 0; static struct avc_callback_node *avc_callbacks; static struct kmem_cache *avc_node_cachep; @@ -431,8 +432,10 @@ static int avc_latest_notif_update(int s ret = -EAGAIN; } } else { - if (seqno > avc_cache.latest_notif) + if (seqno > avc_cache.latest_notif) { avc_cache.latest_notif = seqno; + policy_seqno = seqno; + } } spin_unlock_irqrestore(¬if_lock, flag); 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 2007-09-06 16:08:36.000000000 +0900 @@ -84,6 +84,7 @@ extern unsigned int policydb_loaded_version; extern int selinux_nlmsg_lookup(u16 sclass, u16 nlmsg_type, u32 *perm); extern int selinux_compat_net; +extern u32 policy_seqno; #ifdef CONFIG_SECURITY_SELINUX_DEVELOP int selinux_enforcing = 0; @@ -220,6 +221,8 @@ static int file_alloc_security(struct fi fsec->file = file; fsec->sid = tsec->sid; + fsec->tsid = tsec->sid; + fsec->pseqno = policy_seqno; fsec->fown_sid = tsec->sid; file->f_security = fsec; @@ -2458,7 +2461,7 @@ static int selinux_inode_listsecurity(st /* file security operations */ -static int selinux_file_permission(struct file *file, int mask) +static int do_selinux_file_permission(struct file *file, int mask) { int rc; struct inode *inode = file->f_path.dentry->d_inode; @@ -2480,6 +2483,43 @@ 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->tsid) { + if (tsec->sid != fsec->sid) { + struct vfsmount *mnt = file->f_path.mnt; + struct dentry *dentry = file->f_path.dentry; + struct avc_audit_data ad; + int rc; + AVC_AUDIT_DATA_INIT(&ad, FS); + ad.u.fs.mnt = mnt; + ad.u.fs.dentry = dentry; + rc = avc_has_perm(tsec->sid, fsec->sid, + SECCLASS_FD, + FD__USE, + &ad); + if (rc) + return rc; + } + return do_selinux_file_permission(file, mask); + } + + if (fsec->isid == isec->sid && fsec->pseqno == policy_seqno) + return selinux_netlbl_inode_permission(inode, mask); + + return do_selinux_file_permission(file, mask); +} + static int selinux_file_alloc_security(struct file *file) { return file_alloc_security(file); @@ -2715,6 +2755,16 @@ 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, int flags) +{ + struct file_security_struct *fsec; + struct inode_security_struct *isec; + fsec = file->f_security; + isec = file->f_path.dentry->d_inode->i_security; + fsec->isid = isec->sid; + return 0; +} + /* task security operations */ static int selinux_task_create(unsigned long clone_flags) @@ -4780,6 +4830,8 @@ 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/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 2007-09-06 14:58:11.000000000 +0900 @@ -53,6 +53,9 @@ 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 tsid; /* SID of task at the time of file open*/ + 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 2007-09-06 15:12:29.000000000 +0900 @@ -698,6 +698,11 @@ static struct file *__dentry_open(struct if (!open && f->f_op) open = f->f_op->open; + + error = security_dentry_open(f, flags); + if (error) + goto cleanup_all; + if (open) { error = open(inode, f); if (error) 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 2007-09-06 15:22:39.000000000 +0900 @@ -503,6 +503,11 @@ struct request_sock; * @file contains the file structure being received. * Return 0 if permission is granted. * + * Security hook for dentry + * + * @dentry_open + * Check permission or get additional information before opening dentry. + * * Security hooks for task operations. * * @task_create: @@ -1253,6 +1258,7 @@ 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 flags); int (*task_create) (unsigned long clone_flags); int (*task_alloc_security) (struct task_struct * p); @@ -1854,6 +1860,11 @@ static inline int security_file_receive return security_ops->file_receive (file); } +static inline int security_dentry_open (struct file *file, int flags) +{ + return security_ops->dentry_open (file, flags); +} + static inline int security_task_create (unsigned long clone_flags) { return security_ops->task_create (clone_flags); Regards, -- Yuichi Nakamura Hitachi Software Engineering Co., Ltd. Japan SELinux Users Group(JSELUG): http://www.selinux.gr.jp/ SELinux Policy Editor: http://seedit.sourceforge.net/
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