Re: [PATCH ghak90 V7 04/21] audit: convert to contid list to check for orch/engine ownership

On 2019-09-26 10:46, Neil Horman wrote: > On Wed, Sep 18, 2019 at 09:22:21PM -0400, Richard Guy Briggs wrote: > > Store the audit container identifier in a refcounted kernel object that > > is added to the master list of audit container identifiers. This will > > allow multiple container orchestrators/engines to work on the same > > machine without danger of inadvertantly re-using an existing identifier. > > It will also allow an orchestrator to inject a process into an existing > > container by checking if the original container owner is the one > > injecting the task. A hash table list is used to optimize searches. > > > > Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > > --- > > include/linux/audit.h | 26 ++++++++++++++-- > > kernel/audit.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++--- > > kernel/audit.h | 8 +++++ > > 3 files changed, 112 insertions(+), 8 deletions(-) > > > > diff --git a/include/linux/audit.h b/include/linux/audit.h > > index f2e3b81f2942..e317807cdd3e 100644 > > --- a/include/linux/audit.h > > +++ b/include/linux/audit.h > > @@ -95,10 +95,18 @@ struct audit_ntp_data { > > struct audit_ntp_data {}; > > #endif > > > > +struct audit_cont { > > + struct list_head list; > > + u64 id; > > + struct task_struct *owner; > > + refcount_t refcount; > > + struct rcu_head rcu; > > +}; > > + > > struct audit_task_info { > > kuid_t loginuid; > > unsigned int sessionid; > > - u64 contid; > > + struct audit_cont *cont; > > #ifdef CONFIG_AUDITSYSCALL > > struct audit_context *ctx; > > #endif > > @@ -203,11 +211,15 @@ static inline unsigned int audit_get_sessionid(struct task_struct *tsk) > > > > static inline u64 audit_get_contid(struct task_struct *tsk) > > { > > - if (!tsk->audit) > > + if (!tsk->audit || !tsk->audit->cont) > > return AUDIT_CID_UNSET; > > - return tsk->audit->contid; > > + return tsk->audit->cont->id; > > } > > > > +extern struct audit_cont *audit_cont(struct task_struct *tsk); > > + > > +extern void audit_cont_put(struct audit_cont *cont); > > + > I see that you manual increment this refcount at various call sites, why > no corresponding audit_contid_hold function? I was trying to avoid the get function due to having one site where I needed the pointer for later but didn't need a refcount to it so that I could release the refcount it if it was replaced by another cont object. A hold function would just contain one line that would call the refcount_inc(). If I did convert things over to a get function, it would hide some of this extra conditional code in the main calling function, but in one place I could just call put immediately to neutralize that unneeded refcount.

Would you see any issue with that extra get/put refcount that would only happen in the case of changing a contid in a nesting situation?

> Neil > > > extern u32 audit_enabled; > > > > extern int audit_signal_info(int sig, struct task_struct *t); > > @@ -277,6 +289,14 @@ static inline u64 audit_get_contid(struct task_struct *tsk) > > return AUDIT_CID_UNSET; > > } > > > > +static inline struct audit_cont *audit_cont(struct task_struct *tsk) > > +{ > > + return NULL; > > +} > > + > > +static inline void audit_cont_put(struct audit_cont *cont) > > +{ } > > + > > #define audit_enabled AUDIT_OFF > > > > static inline int audit_signal_info(int sig, struct task_struct *t) > > diff --git a/kernel/audit.c b/kernel/audit.c > > index a36ea57cbb61..ea0899130cc1 100644 > > --- a/kernel/audit.c > > +++ b/kernel/audit.c > > @@ -137,6 +137,8 @@ struct audit_net { > > > > /* Hash for inode-based rules */ > > struct list_head audit_inode_hash[AUDIT_INODE_BUCKETS]; > > +/* Hash for contid-based rules */ > > +struct list_head audit_contid_hash[AUDIT_CONTID_BUCKETS]; > > > > static struct kmem_cache *audit_buffer_cache; > > > > @@ -204,6 +206,8 @@ struct audit_reply { > > > > static struct kmem_cache *audit_task_cache; > > > > +static DEFINE_SPINLOCK(audit_contid_list_lock); > > + > > void __init audit_task_init(void) > > { > > audit_task_cache = kmem_cache_create("audit_task", > > @@ -231,7 +235,9 @@ int audit_alloc(struct task_struct *tsk) > > } > > info->loginuid = audit_get_loginuid(current); > > info->sessionid = audit_get_sessionid(current); > > - info->contid = audit_get_contid(current); > > + info->cont = audit_cont(current); > > + if (info->cont) > > + refcount_inc(&info->cont->refcount); > > tsk->audit = info; > > > > ret = audit_alloc_syscall(tsk); > > @@ -246,7 +252,7 @@ int audit_alloc(struct task_struct *tsk) > > struct audit_task_info init_struct_audit = { > > .loginuid = INVALID_UID, > > .sessionid = AUDIT_SID_UNSET, > > - .contid = AUDIT_CID_UNSET, > > + .cont = NULL, > > #ifdef CONFIG_AUDITSYSCALL > > .ctx = NULL, > > #endif > > @@ -266,6 +272,9 @@ void audit_free(struct task_struct *tsk) > > /* Freeing the audit_task_info struct must be performed after > > * audit_log_exit() due to need for loginuid and sessionid. > > */ > > + spin_lock(&audit_contid_list_lock); > > + audit_cont_put(tsk->audit->cont); > > + spin_unlock(&audit_contid_list_lock); > > info = tsk->audit; > > tsk->audit = NULL; > > kmem_cache_free(audit_task_cache, info); > > @@ -1657,6 +1666,9 @@ static int __init audit_init(void) > > for (i = 0; i < AUDIT_INODE_BUCKETS; i++) > > INIT_LIST_HEAD(&audit_inode_hash[i]); > > > > + for (i = 0; i < AUDIT_CONTID_BUCKETS; i++) > > + INIT_LIST_HEAD(&audit_contid_hash[i]); > > + > > mutex_init(&audit_cmd_mutex.lock); > > audit_cmd_mutex.owner = NULL; > > > > @@ -2356,6 +2368,32 @@ int audit_signal_info(int sig, struct task_struct *t) > > return audit_signal_info_syscall(t); > > } > > > > +struct audit_cont *audit_cont(struct task_struct *tsk) > > +{ > > + if (!tsk->audit || !tsk->audit->cont) > > + return NULL; > > + return tsk->audit->cont; > > +} > > + > > +/* audit_contid_list_lock must be held by caller */ > > +void audit_cont_put(struct audit_cont *cont) > > +{ > > + if (!cont) > > + return; > > + if (refcount_dec_and_test(&cont->refcount)) { > > + put_task_struct(cont->owner); > > + list_del_rcu(&cont->list); > > + kfree_rcu(cont, rcu); > > + } > > +} > > + > > +static struct task_struct *audit_cont_owner(struct task_struct *tsk) > > +{ > > + if (tsk->audit && tsk->audit->cont) > > + return tsk->audit->cont->owner; > > + return NULL; > > +} > > + > > /* > > * audit_set_contid - set current task's audit contid > > * @task: target task > > @@ -2382,9 +2420,12 @@ int audit_set_contid(struct task_struct *task, u64 contid) > > } > > oldcontid = audit_get_contid(task); > > read_lock(&tasklist_lock); > > - /* Don't allow the audit containerid to be unset */ > > + /* Don't allow the contid to be unset */ > > if (!audit_contid_valid(contid)) > > rc = -EINVAL; > > + /* Don't allow the contid to be set to the same value again */ > > + else if (contid == oldcontid) { > > + rc = -EADDRINUSE; > > /* if we don't have caps, reject */ > > else if (!capable(CAP_AUDIT_CONTROL)) > > rc = -EPERM; > > @@ -2397,8 +2438,43 @@ int audit_set_contid(struct task_struct *task, u64 contid) > > else if (audit_contid_set(task)) > > rc = -ECHILD; > > read_unlock(&tasklist_lock); > > - if (!rc) > > - task->audit->contid = contid; > > + if (!rc) { > > + struct audit_cont *oldcont = audit_cont(task); > > + struct audit_cont *cont = NULL; > > + struct audit_cont *newcont = NULL; > > + int h = audit_hash_contid(contid); > > + > > + spin_lock(&audit_contid_list_lock); > > + list_for_each_entry_rcu(cont, &audit_contid_hash[h], list) > > + if (cont->id == contid) { > > + /* task injection to existing container */ > > + if (current == cont->owner) { > > + refcount_inc(&cont->refcount); > > + newcont = cont; > > + } else { > > + rc = -ENOTUNIQ; > > + goto conterror; > > + } > > + } > > + if (!newcont) { > > + newcont = kmalloc(sizeof(struct audit_cont), GFP_ATOMIC); > > + if (newcont) { > > + INIT_LIST_HEAD(&newcont->list); > > + newcont->id = contid; > > + get_task_struct(current); > > + newcont->owner = current; > > + refcount_set(&newcont->refcount, 1); > > + list_add_rcu(&newcont->list, &audit_contid_hash[h]); > > + } else { > > + rc = -ENOMEM; > > + goto conterror; > > + } > > + } > > + task->audit->cont = newcont; > > + audit_cont_put(oldcont); > > +conterror: > > + spin_unlock(&audit_contid_list_lock); > > + } > > task_unlock(task); > > > > if (!audit_enabled) > > diff --git a/kernel/audit.h b/kernel/audit.h > > index 16bd03b88e0d..e4a31aa92dfe 100644 > > --- a/kernel/audit.h > > +++ b/kernel/audit.h > > @@ -211,6 +211,14 @@ static inline int audit_hash_ino(u32 ino) > > return (ino & (AUDIT_INODE_BUCKETS-1)); > > } > > > > +#define AUDIT_CONTID_BUCKETS 32 > > +extern struct list_head audit_contid_hash[AUDIT_CONTID_BUCKETS]; > > + > > +static inline int audit_hash_contid(u64 contid) > > +{ > > + return (contid & (AUDIT_CONTID_BUCKETS-1)); > > +} > > + > > /* Indicates that audit should log the full pathname. */ > > #define AUDIT_NAME_FULL -1 > > > > -- > > 1.8.3.1 > > > > - RGB -- Richard Guy Briggs <rgb(a)redhat.com&gt; Sr. S/W Engineer, Kernel Security, Base Operating Systems Remote, Ottawa, Red Hat Canada IRC: rgb, SunRaycer Voice: +1.647.777.2635, Internal: (81) 32635