[PATCH] [RFC] SELINUX: Remove obsolete deferred inode security init list.
Konstantin Meskhidze
konstantin.meskhidze at huawei.com
Mon Nov 14 11:18:44 UTC 2022
From: Alexander Kozhevnikov <alexander.kozhevnikov at huawei-partners.com>
This patch is a proposed code optimization for SELinux:
1) Each inode has SELinux security structure attached
to it, this one need to be initialized at some point.
2) This initialization is done by the function
inode_doinit_with_dentry ( ).
3) In the kernel releases started from some point in the past
this function (2) is always called normally from function
__inode_security_revalidate ( ).
4) Which in turn is always called from inode_security ( ), which
is a base point for any selinux calls and always called on
any access to any inode except a few special cases when
_inode_security_novalidate ( ) is used.
5) Inode security structure initialization can be done only after
SELinux is fully initialized and policy is loaded.
6) So, for this purpose there was a special defeferred inode security
initialization list protected by a spinlock implemented, which was
populated instead of isec initialization in function
inode_doinit_with_dentry ( ), if it was called before SELinux full
initialization, and processed at the time when SELinux policy load
occurred by calling again inode_doinit_with_dentry ( ) on each inode
in this list.
7) This list was a part of a default initialization logic before (3) was
implemented, but now, taking into account new mechanism implemented
with current approach of inode security revalidation on each access
(4)-(3)-(2), it looks obsolete and not needed anymore.
8) So deferred initialization, this list and code associated with it can
be safely removed now, as anyway, if inode isec was not initialized
before it will be processed on any next inode access.
9) There are two possible positive consequences from this removal:
a. More clean and simple code, less memory consumption;
b. This deferred initialization in some cases (for example SELinux
was switched on manually after system was up quite a long time)
could take some significant time to process, i.e. system looks
hung for some notable time. And now this is avoided.
Signed-off-by: Alexander Kozhevnikov <alexander.kozhevnikov at huawei-partners.com>
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze at huawei.com>
---
security/selinux/hooks.c | 70 ++++---------------------------
security/selinux/include/objsec.h | 3 --
2 files changed, 7 insertions(+), 66 deletions(-)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index f553c370397e..c93b5621d735 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -316,27 +316,7 @@ static struct inode_security_struct *backing_inode_security(struct dentry *dentr
static void inode_free_security(struct inode *inode)
{
- struct inode_security_struct *isec = selinux_inode(inode);
- struct superblock_security_struct *sbsec;
-
- if (!isec)
- return;
- sbsec = selinux_superblock(inode->i_sb);
- /*
- * As not all inode security structures are in a list, we check for
- * empty list outside of the lock to make sure that we won't waste
- * time taking a lock doing nothing.
- *
- * The list_del_init() function can be safely called more than once.
- * It should not be possible for this function to be called with
- * concurrent list_add(), but for better safety against future changes
- * in the code, we use list_empty_careful() here.
- */
- if (!list_empty_careful(&isec->list)) {
- spin_lock(&sbsec->isec_lock);
- list_del_init(&isec->list);
- spin_unlock(&sbsec->isec_lock);
- }
+/* NOTHING TO DO AFTER DEFERRED LIST REMOVAL */
}
struct selinux_mnt_opts {
@@ -551,27 +531,6 @@ static int sb_finish_set_opts(struct super_block *sb)
/* Initialize the root inode. */
rc = inode_doinit_with_dentry(root_inode, root);
- /* Initialize any other inodes associated with the superblock, e.g.
- inodes created prior to initial policy load or inodes created
- during get_sb by a pseudo filesystem that directly
- populates itself. */
- spin_lock(&sbsec->isec_lock);
- while (!list_empty(&sbsec->isec_head)) {
- struct inode_security_struct *isec =
- list_first_entry(&sbsec->isec_head,
- struct inode_security_struct, list);
- struct inode *inode = isec->inode;
- list_del_init(&isec->list);
- spin_unlock(&sbsec->isec_lock);
- inode = igrab(inode);
- if (inode) {
- if (!IS_PRIVATE(inode))
- inode_doinit_with_dentry(inode, NULL);
- iput(inode);
- }
- spin_lock(&sbsec->isec_lock);
- }
- spin_unlock(&sbsec->isec_lock);
return rc;
}
@@ -1378,6 +1337,10 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
if (isec->initialized == LABEL_INITIALIZED)
return 0;
+ sbsec = selinux_superblock(inode->i_sb);
+ if (!(sbsec->flags & SE_SBINITIALIZED))
+ return 0;
+
spin_lock(&isec->lock);
if (isec->initialized == LABEL_INITIALIZED)
goto out_unlock;
@@ -1385,18 +1348,6 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
if (isec->sclass == SECCLASS_FILE)
isec->sclass = inode_mode_to_security_class(inode->i_mode);
- sbsec = selinux_superblock(inode->i_sb);
- if (!(sbsec->flags & SE_SBINITIALIZED)) {
- /* Defer initialization until selinux_complete_init,
- after the initial policy is loaded and the security
- server is ready to handle calls. */
- spin_lock(&sbsec->isec_lock);
- if (list_empty(&isec->list))
- list_add(&isec->list, &sbsec->isec_head);
- spin_unlock(&sbsec->isec_lock);
- goto out_unlock;
- }
-
sclass = isec->sclass;
task_sid = isec->task_sid;
sid = isec->sid;
@@ -1430,9 +1381,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
if (!dentry) {
/*
* this is can be hit on boot when a file is accessed
- * before the policy is loaded. When we load policy we
- * may find inodes that have no dentry on the
- * sbsec->isec_head list. No reason to complain as these
+ * before the policy is loaded. No reason to complain as these
* will get fixed up the next time we go through
* inode_doinit with a dentry, before these inodes could
* be used again by userspace.
@@ -1486,9 +1435,7 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
}
/*
* This can be hit on boot when a file is accessed
- * before the policy is loaded. When we load policy we
- * may find inodes that have no dentry on the
- * sbsec->isec_head list. No reason to complain as
+ * before the policy is loaded. No reason to complain as
* these will get fixed up the next time we go through
* inode_doinit() with a dentry, before these inodes
* could be used again by userspace.
@@ -2543,8 +2490,6 @@ static int selinux_sb_alloc_security(struct super_block *sb)
struct superblock_security_struct *sbsec = selinux_superblock(sb);
mutex_init(&sbsec->lock);
- INIT_LIST_HEAD(&sbsec->isec_head);
- spin_lock_init(&sbsec->isec_lock);
sbsec->sid = SECINITSID_UNLABELED;
sbsec->def_sid = SECINITSID_FILE;
sbsec->mntpoint_sid = SECINITSID_UNLABELED;
@@ -2808,7 +2753,6 @@ static int selinux_inode_alloc_security(struct inode *inode)
u32 sid = current_sid();
spin_lock_init(&isec->lock);
- INIT_LIST_HEAD(&isec->list);
isec->inode = inode;
isec->sid = SECINITSID_UNLABELED;
isec->sclass = SECCLASS_FILE;
diff --git a/security/selinux/include/objsec.h b/security/selinux/include/objsec.h
index 2953132408bf..58f752af38cf 100644
--- a/security/selinux/include/objsec.h
+++ b/security/selinux/include/objsec.h
@@ -45,7 +45,6 @@ enum label_initialized {
struct inode_security_struct {
struct inode *inode; /* back pointer to inode object */
- struct list_head list; /* list of inode_security_struct */
u32 task_sid; /* SID of creating task */
u32 sid; /* SID of this object */
u16 sclass; /* security class of this object */
@@ -67,8 +66,6 @@ struct superblock_security_struct {
unsigned short behavior; /* labeling behavior */
unsigned short flags; /* which mount options were specified */
struct mutex lock;
- struct list_head isec_head;
- spinlock_t isec_lock;
};
struct msg_security_struct {
--
2.31.1
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