| Message ID | 20221213033948.73512-2-alexander.kozhevnikov@huawei-partners.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | Paul Moore |
| Headers | show |
| Series | SELINUX: Remove obsolete deferred inode security | expand |
On Mon, Dec 12, 2022 at 10:40 PM Alexander Kozhevnikov <alexander.kozhevnikov@huawei-partners.com> wrote: > > 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) Another case for calling inode_doinit_with_dentry( ) is when a new > dentry is created. This is done by call from d_instantiate( ). When > the deferred initialization list is removed it would be useful to > also check for SELinux initialization status here before calling > inode_doinit_with_dentry( ) like it is done in > __inode_security_revalidate( ). > 10) 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@huawei-partners.com> > --- > security/selinux/hooks.c | 91 ++++--------------------------- > security/selinux/include/objsec.h | 3 - > 2 files changed, 11 insertions(+), 83 deletions(-) Merged into selinux/next with some minor style and grammar fixes, thanks Alexander!
On Fri, Jan 6, 2023 at 3:30 PM Paul Moore <paul@paul-moore.com> wrote: > > On Mon, Dec 12, 2022 at 10:40 PM Alexander Kozhevnikov > <alexander.kozhevnikov@huawei-partners.com> wrote: > > > > 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) Another case for calling inode_doinit_with_dentry( ) is when a new > > dentry is created. This is done by call from d_instantiate( ). When > > the deferred initialization list is removed it would be useful to > > also check for SELinux initialization status here before calling > > inode_doinit_with_dentry( ) like it is done in > > __inode_security_revalidate( ). > > 10) 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@huawei-partners.com> > > --- > > security/selinux/hooks.c | 91 ++++--------------------------- > > security/selinux/include/objsec.h | 3 - > > 2 files changed, 11 insertions(+), 83 deletions(-) > > Merged into selinux/next with some minor style and grammar fixes, > thanks Alexander! Unfortunately I just had to back this commit out of selinux/next as the automated testing using the selinux-testsuite failed on my Fedora Rawhide test system failed. Please verify that this patch passes the selinux-testsuite on a modern Fedora Rawhide install using Linux v6.2-rc2 as a base.
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index f553c370397e..88da9068a29e 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -314,31 +314,6 @@ static struct inode_security_struct *backing_inode_security(struct dentry *dentr return selinux_inode(inode); } -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); - } -} - struct selinux_mnt_opts { u32 fscontext_sid; u32 context_sid; @@ -549,30 +524,7 @@ static int sb_finish_set_opts(struct super_block *sb) sbsec->flags &= ~SBLABEL_MNT; /* 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; + return inode_doinit_with_dentry(root_inode, root); } static int bad_option(struct superblock_security_struct *sbsec, char flag, @@ -1378,6 +1330,10 @@ 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 +1341,6 @@ 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; @@ -1429,12 +1373,10 @@ 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 + * This is can be hit on boot when a file is accessed + * 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 + * inode_doinit_with_dentry(), before these inodes could * be used again by userspace. */ goto out_invalid; @@ -1486,11 +1428,9 @@ 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 + * inode_doinit_with_dentry(), before these inodes * could be used again by userspace. */ if (!dentry) @@ -2543,8 +2483,6 @@ 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 +2746,6 @@ 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; @@ -2818,11 +2755,6 @@ static int selinux_inode_alloc_security(struct inode *inode) return 0; } -static void selinux_inode_free_security(struct inode *inode) -{ - inode_free_security(inode); -} - static int selinux_dentry_init_security(struct dentry *dentry, int mode, const struct qstr *name, const char **xattr_name, void **ctx, @@ -6325,7 +6257,7 @@ static void selinux_ipc_getsecid(struct kern_ipc_perm *ipcp, u32 *secid) static void selinux_d_instantiate(struct dentry *dentry, struct inode *inode) { - if (inode) + if (selinux_initialized(&selinux_state) && inode) inode_doinit_with_dentry(inode, dentry); } @@ -7067,7 +6999,6 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(dentry_init_security, selinux_dentry_init_security), LSM_HOOK_INIT(dentry_create_files_as, selinux_dentry_create_files_as), - LSM_HOOK_INIT(inode_free_security, selinux_inode_free_security), LSM_HOOK_INIT(inode_init_security, selinux_inode_init_security), LSM_HOOK_INIT(inode_init_security_anon, selinux_inode_init_security_anon), LSM_HOOK_INIT(inode_create, selinux_inode_create), 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 {
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) Another case for calling inode_doinit_with_dentry( ) is when a new dentry is created. This is done by call from d_instantiate( ). When the deferred initialization list is removed it would be useful to also check for SELinux initialization status here before calling inode_doinit_with_dentry( ) like it is done in __inode_security_revalidate( ). 10) 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@huawei-partners.com> --- security/selinux/hooks.c | 91 ++++--------------------------- security/selinux/include/objsec.h | 3 - 2 files changed, 11 insertions(+), 83 deletions(-)