Re: [PATCH -mm] fs.h: ifdef security fields

From: Alexey Dobriyan
Date: Sun Aug 06 2006 - 01:21:03 EST

On Sat, Aug 05, 2006 at 11:25:49PM -0500, Serge E. Hallyn wrote:
> Quoting Alexey Dobriyan (adobriyan@xxxxxxxxx):
> > [BSD security levels are deleted in -mm, assuming this below]
> >
> > The only user of i_security, f_security, s_security fields is SELinux,
> > so ifdef them with CONFIG_SECURITY_SELINUX. Following Stephen Smalley's
> The SLIM security module, which is trying to get upstream, uses at least
> i_security and f_security.

OK, see it.

> The Argus module supposedly being submitted "soon" which is used in
> their LSPP product, surely must use them all.

If they're going to use struct fown_struct::security, they'll just
re-add it. Preferably under different name, so grepping for it won't be

> Maybe you still want to make these CONFIG_SECURITY_SELINUX until the
> other modules are upstreamed, but I just wanted to make sure you knew
> other modules, trying to get upstream, are using them.
> Personally I'd say these are a core part of the LSM framework, and if
> you don't want LSM, compile it out.

That's what I'm trying to do. This time for real. ;-)

> But since I realize that using only
> capabilities must be a pretty common case, how about just adding a
> config option CONFIG_SECURITY_OBJFIELDS, which is auto-enabled with
> SELINUX and default off, which hides these fields instead?

Ahh, this is getting more and more complex, so I'll just put it under
CONFIG_SECURITY and leave it.

> Patch should be trivial, and I can aim to send one tomorrow.

No need.
[PATCH] fs.h: ifdef security fields

[assuming BSD security levels are deleted]
The only user of i_security, f_security, s_security fields is SELinux,
however, quite a few security modules are trying to get into kernel.
So, wrap them under CONFIG_SECURITY. Adding config option for each
security field is likely an overkill.

Following Stephen Smalley's suggestion, i_security initialization is
moved to security_inode_alloc() to not clutter core code with ifdefs
and make alloc_inode() codepath tiny little bit smaller and faster.

The user of (highly greppable) struct fown_struct::security field is
still to be found. I've checked every "fown_struct" and every "f_owner"
occurence. Additionally it's removal doesn't break i386 allmodconfig

struct inode, struct file, struct super_block, struct fown_struct
become smaller.

P.S. Combined with two reiserfs inode shrinking patches sent to
linux-fsdevel, I can finally suck 12 reiserfs inodes into one page.


-ext2_inode_cache 388 10
+ext2_inode_cache 384 10
-inode_cache 280 14
+inode_cache 276 14
-proc_inode_cache 296 13
+proc_inode_cache 292 13
-reiser_inode_cache 336 11
+reiser_inode_cache 332 12 <=
-shmem_inode_cache 372 10
+shmem_inode_cache 368 10

Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>

fs/inode.c | 1 -
include/linux/fs.h | 8 ++++++--
include/linux/security.h | 1 +
3 files changed, 7 insertions(+), 3 deletions(-)

--- a/fs/inode.c
+++ b/fs/inode.c
@@ -133,7 +133,6 @@ #endif
inode->i_bdev = NULL;
inode->i_cdev = NULL;
inode->i_rdev = 0;
- inode->i_security = NULL;
inode->dirtied_when = 0;
if (security_inode_alloc(inode)) {
if (inode->i_sb->s_op->destroy_inode)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -552,7 +552,9 @@ struct inode {
unsigned int i_flags;

atomic_t i_writecount;
void *i_security;
union {
void *generic_ip;
} u;
@@ -645,7 +647,6 @@ struct fown_struct {
rwlock_t lock; /* protects pid, uid, euid fields */
int pid; /* pid or -pgrp where SIGIO should be sent */
uid_t uid, euid; /* uid/euid of process setting the owner */
- void *security;
int signum; /* posix.1b rt signal to be delivered on IO */

@@ -688,8 +689,9 @@ struct file {
struct file_ra_state f_ra;

unsigned long f_version;
void *f_security;
/* needed for tty driver, and maybe others */
void *private_data;

@@ -877,7 +879,9 @@ struct super_block {
int s_syncing;
int s_need_sync_fs;
atomic_t s_active;
void *s_security;
struct xattr_handler **s_xattr;

struct list_head s_inodes; /* all inodes */
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1549,6 +1549,7 @@ static inline void security_sb_post_pivo

static inline int security_inode_alloc (struct inode *inode)
+ inode->i_security = NULL;
return security_ops->inode_alloc_security (inode);

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