[PATCH ghak90 v10 01/11] audit: collect audit task parameters

From: Richard Guy Briggs
Date: Mon Dec 21 2020 - 11:59:16 EST

The audit-related parameters in struct task_struct should ideally be
collected together and accessed through a standard audit API and the audit
structures made opaque to other kernel subsystems.

Collect the existing loginuid, sessionid and audit_context together in a
new opaque struct audit_task_info called "audit" in struct task_struct.

Use kmem_cache to manage this pool of memory.
Un-inline audit_free() to be able to always recover that memory.

Please see the upstream github issues
https://github.com/linux-audit/audit-kernel/issues/81
https://github.com/linux-audit/audit-kernel/issues/90

Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Reviewed-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
---
fs/io-wq.c | 8 +--
fs/io_uring.c | 16 ++---
include/linux/audit.h | 49 +++++---------
include/linux/sched.h | 7 +-
init/init_task.c | 3 +-
init/main.c | 2 +
kernel/audit.c | 154 +++++++++++++++++++++++++++++++++++++++++-
kernel/audit.h | 7 ++
kernel/auditsc.c | 24 ++++---
kernel/fork.c | 1 -
10 files changed, 205 insertions(+), 66 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 02894df7656d..1c39207f3ffc 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -496,8 +496,8 @@ static void io_impersonate_work(struct io_worker *worker,
current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
io_wq_switch_blkcg(worker, work);
#ifdef CONFIG_AUDIT
- current->loginuid = work->identity->loginuid;
- current->sessionid = work->identity->sessionid;
+ audit_set_loginuid_iouring(work->identity->loginuid);
+ audit_set_sessionid_iouring(work->identity->sessionid);
#endif
}

@@ -512,8 +512,8 @@ static void io_assign_current_work(struct io_worker *worker,
}

#ifdef CONFIG_AUDIT
- current->loginuid = KUIDT_INIT(AUDIT_UID_UNSET);
- current->sessionid = AUDIT_SID_UNSET;
+ audit_set_loginuid_iouring(KUIDT_INIT(AUDIT_UID_UNSET));
+ audit_set_sessionid_iouring(AUDIT_SID_UNSET);
#endif

spin_lock_irq(&worker->lock);
diff --git a/fs/io_uring.c b/fs/io_uring.c
index b42dfa0243bf..a1e178d8b040 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1064,8 +1064,8 @@ static void io_init_identity(struct io_identity *id)
id->fs = current->fs;
id->fsize = rlimit(RLIMIT_FSIZE);
#ifdef CONFIG_AUDIT
- id->loginuid = current->loginuid;
- id->sessionid = current->sessionid;
+ id->loginuid = audit_get_loginuid(current);
+ id->sessionid = audit_get_sessionid(current);
#endif
refcount_set(&id->count, 1);
}
@@ -1335,8 +1335,8 @@ static bool io_grab_identity(struct io_kiocb *req)
req->work.flags |= IO_WQ_WORK_CREDS;
}
#ifdef CONFIG_AUDIT
- if (!uid_eq(current->loginuid, id->loginuid) ||
- current->sessionid != id->sessionid)
+ if (!uid_eq(audit_get_loginuid(current), id->loginuid) ||
+ audit_get_sessionid(current) != id->sessionid)
return false;
#endif
if (!(req->work.flags & IO_WQ_WORK_FS) &&
@@ -6771,8 +6771,8 @@ static int io_sq_thread(void *data)
}
io_sq_thread_associate_blkcg(ctx, &cur_css);
#ifdef CONFIG_AUDIT
- current->loginuid = ctx->loginuid;
- current->sessionid = ctx->sessionid;
+ audit_set_loginuid_iouring(ctx->loginuid);
+ audit_set_sessionid_iouring(ctx->sessionid);
#endif

ret |= __io_sq_thread(ctx, start_jiffies, cap_entries);
@@ -9205,8 +9205,8 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p,
ctx->user = user;
ctx->creds = get_current_cred();
#ifdef CONFIG_AUDIT
- ctx->loginuid = current->loginuid;
- ctx->sessionid = current->sessionid;
+ ctx->loginuid = audit_get_loginuid(current);
+ ctx->sessionid = audit_get_sessionid(current);
#endif
ctx->sqo_task = get_task_struct(current);

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 82b7c1116a85..515cc89a7e0c 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -154,6 +154,9 @@ struct filename;
#ifdef CONFIG_AUDIT
/* These are defined in audit.c */
/* Public API */
+extern int audit_alloc(struct task_struct *task);
+extern void audit_free(struct task_struct *task);
+extern void __init audit_task_init(void);
extern __printf(4, 5)
void audit_log(struct audit_context *ctx, gfp_t gfp_mask, int type,
const char *fmt, ...);
@@ -194,22 +197,26 @@ extern int audit_rule_change(int type, int seq, void *data, size_t datasz);
extern int audit_list_rules_send(struct sk_buff *request_skb, int seq);

extern int audit_set_loginuid(kuid_t loginuid);
+extern void audit_set_loginuid_iouring(kuid_t loginuid);

-static inline kuid_t audit_get_loginuid(struct task_struct *tsk)
-{
- return tsk->loginuid;
-}
+extern kuid_t audit_get_loginuid(struct task_struct *tsk);

-static inline unsigned int audit_get_sessionid(struct task_struct *tsk)
-{
- return tsk->sessionid;
-}
+extern unsigned int audit_get_sessionid(struct task_struct *tsk);
+extern void audit_set_sessionid_iouring(unsigned int sessionid);

extern u32 audit_enabled;

extern int audit_signal_info(int sig, struct task_struct *t);

#else /* CONFIG_AUDIT */
+static inline int audit_alloc(struct task_struct *task)
+{
+ return 0;
+}
+static inline void audit_free(struct task_struct *task)
+{ }
+static inline void __init audit_task_init(void)
+{ }
static inline __printf(4, 5)
void audit_log(struct audit_context *ctx, gfp_t gfp_mask, int type,
const char *fmt, ...)
@@ -285,8 +292,6 @@ static inline int audit_signal_info(int sig, struct task_struct *t)

/* These are defined in auditsc.c */
/* Public API */
-extern int audit_alloc(struct task_struct *task);
-extern void __audit_free(struct task_struct *task);
extern void __audit_syscall_entry(int major, unsigned long a0, unsigned long a1,
unsigned long a2, unsigned long a3);
extern void __audit_syscall_exit(int ret_success, long ret_value);
@@ -303,26 +308,14 @@ extern void audit_seccomp_actions_logged(const char *names,
const char *old_names, int res);
extern void __audit_ptrace(struct task_struct *t);

-static inline void audit_set_context(struct task_struct *task, struct audit_context *ctx)
-{
- task->audit_context = ctx;
-}
-
-static inline struct audit_context *audit_context(void)
-{
- return current->audit_context;
-}
+extern struct audit_context *audit_context(void);

static inline bool audit_dummy_context(void)
{
void *p = audit_context();
return !p || *(int *)p;
}
-static inline void audit_free(struct task_struct *task)
-{
- if (unlikely(task->audit_context))
- __audit_free(task);
-}
+
static inline void audit_syscall_entry(int major, unsigned long a0,
unsigned long a1, unsigned long a2,
unsigned long a3)
@@ -550,12 +543,6 @@ static inline void audit_log_nfcfg(const char *name, u8 af,
extern int audit_n_rules;
extern int audit_signals;
#else /* CONFIG_AUDITSYSCALL */
-static inline int audit_alloc(struct task_struct *task)
-{
- return 0;
-}
-static inline void audit_free(struct task_struct *task)
-{ }
static inline void audit_syscall_entry(int major, unsigned long a0,
unsigned long a1, unsigned long a2,
unsigned long a3)
@@ -566,8 +553,6 @@ static inline bool audit_dummy_context(void)
{
return true;
}
-static inline void audit_set_context(struct task_struct *task, struct audit_context *ctx)
-{ }
static inline struct audit_context *audit_context(void)
{
return NULL;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 063cd120b459..b28348868b27 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -36,7 +36,6 @@
#include <linux/kcsan.h>

/* task_struct member predeclarations (sorted alphabetically): */
-struct audit_context;
struct backing_dev_info;
struct bio_list;
struct blk_plug;
@@ -958,11 +957,7 @@ struct task_struct {
struct callback_head *task_works;

#ifdef CONFIG_AUDIT
-#ifdef CONFIG_AUDITSYSCALL
- struct audit_context *audit_context;
-#endif
- kuid_t loginuid;
- unsigned int sessionid;
+ void *audit;
#endif
struct seccomp seccomp;

diff --git a/init/init_task.c b/init/init_task.c
index a56f0abb63e9..2909c46056e1 100644
--- a/init/init_task.c
+++ b/init/init_task.c
@@ -134,8 +134,7 @@ struct task_struct init_task
.thread_group = LIST_HEAD_INIT(init_task.thread_group),
.thread_node = LIST_HEAD_INIT(init_signals.thread_head),
#ifdef CONFIG_AUDIT
- .loginuid = INVALID_UID,
- .sessionid = AUDIT_SID_UNSET,
+ .audit = NULL,
#endif
#ifdef CONFIG_PERF_EVENTS
.perf_event_mutex = __MUTEX_INITIALIZER(init_task.perf_event_mutex),
diff --git a/init/main.c b/init/main.c
index 130376ec10ba..da821e5ce077 100644
--- a/init/main.c
+++ b/init/main.c
@@ -98,6 +98,7 @@
#include <linux/mem_encrypt.h>
#include <linux/kcsan.h>
#include <linux/init_syscalls.h>
+#include <linux/audit.h>

#include <asm/io.h>
#include <asm/bugs.h>
@@ -1036,6 +1037,7 @@ asmlinkage __visible void __init __no_sanitize_address start_kernel(void)
nsfs_init();
cpuset_init();
cgroup_init();
+ audit_task_init();
taskstats_init_early();
delayacct_init();

diff --git a/kernel/audit.c b/kernel/audit.c
index 1ffc2e059027..2719ca147150 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -208,6 +208,148 @@ struct audit_reply {
struct sk_buff *skb;
};

+struct audit_task_info {
+ kuid_t loginuid;
+ unsigned int sessionid;
+#ifdef CONFIG_AUDITSYSCALL
+ struct audit_context *ctx;
+#endif
+};
+
+static struct kmem_cache *audit_task_cache;
+
+void __init audit_task_init(void)
+{
+ audit_task_cache = kmem_cache_create("audit_task",
+ sizeof(struct audit_task_info),
+ 0, SLAB_PANIC, NULL);
+}
+
+inline kuid_t audit_get_loginuid(struct task_struct *tsk)
+{
+ struct audit_task_info *info = tsk->audit;
+
+ if (!info)
+ return INVALID_UID;
+ return info->loginuid;
+}
+
+inline void audit_set_loginuid_iouring(kuid_t loginuid)
+{
+ struct audit_task_info *info = current->audit;
+
+ if (!info)
+ return;
+ info->loginuid = loginuid;
+}
+
+inline unsigned int audit_get_sessionid(struct task_struct *tsk)
+{
+ struct audit_task_info *info = tsk->audit;
+
+ if (!info)
+ return AUDIT_SID_UNSET;
+ return info->sessionid;
+}
+
+inline void audit_set_sessionid_iouring(unsigned int sessionid)
+{
+ struct audit_task_info *info = current->audit;
+
+ if (!info)
+ return;
+ info->sessionid = sessionid;
+}
+
+inline struct audit_context *_audit_context(struct task_struct *tsk)
+{
+ struct audit_task_info *info = tsk->audit;
+
+ if (!info)
+ return NULL;
+ return info->ctx;
+}
+
+struct audit_context *audit_context(void)
+{
+ return _audit_context(current);
+}
+EXPORT_SYMBOL(audit_context);
+
+static void audit_alloc_task(struct task_struct *tsk)
+{
+ struct audit_task_info *info = tsk->audit;
+
+ if (info && !IS_ERR(info))
+ return;
+ info = kmem_cache_alloc(audit_task_cache, GFP_KERNEL);
+ if (!info) {
+ tsk->audit = ERR_PTR(-ENOMEM);
+ return;
+ }
+ info->loginuid = audit_get_loginuid(current);
+ info->sessionid = audit_get_sessionid(current);
+ tsk->audit = info;
+}
+
+void audit_set_context(struct task_struct *tsk, struct audit_context *ctx)
+{
+ struct audit_task_info *info;
+
+ audit_alloc_task(tsk);
+ info = tsk->audit;
+ if (!IS_ERR(info))
+ info->ctx = ctx;
+ else
+ tsk->audit = NULL;
+}
+
+/**
+ * audit_alloc - allocate an audit info block for a task
+ * @tsk: task
+ *
+ * Call audit_alloc_syscall to filter on the task information and
+ * allocate a per-task audit context if necessary. This is called from
+ * copy_process, so no lock is needed.
+ */
+int audit_alloc(struct task_struct *tsk)
+{
+ int ret = 0;
+
+ tsk->audit = NULL;
+ audit_alloc_task(tsk);
+ if (IS_ERR(tsk->audit)) {
+ ret = PTR_ERR(tsk->audit);
+ tsk->audit = NULL;
+ goto out;
+ }
+ ret = audit_alloc_syscall(tsk);
+ if (ret) {
+ kmem_cache_free(audit_task_cache, tsk->audit);
+ tsk->audit = NULL;
+ }
+out:
+ return ret;
+}
+
+/**
+ * audit_free - free per-task audit info
+ * @tsk: task whose audit info block to free
+ *
+ * Called from copy_process and do_exit
+ */
+void audit_free(struct task_struct *tsk)
+{
+ struct audit_task_info *info = tsk->audit;
+
+ audit_free_syscall(tsk);
+ /* Freeing the audit_task_info struct must be performed after
+ * audit_log_exit() due to need for loginuid and sessionid.
+ */
+ tsk->audit = NULL;
+ kmem_cache_free(audit_task_cache, info);
+}
+
/**
* auditd_test_task - Check to see if a given task is an audit daemon
* @task: the task to check
@@ -2310,6 +2452,7 @@ int audit_set_loginuid(kuid_t loginuid)
unsigned int oldsessionid, sessionid = AUDIT_SID_UNSET;
kuid_t oldloginuid;
int rc;
+ struct audit_task_info *info;

oldloginuid = audit_get_loginuid(current);
oldsessionid = audit_get_sessionid(current);
@@ -2317,6 +2460,12 @@ int audit_set_loginuid(kuid_t loginuid)
rc = audit_set_loginuid_perm(loginuid);
if (rc)
goto out;
+ audit_alloc_task(current);
+ if (IS_ERR(current->audit)) {
+ rc = PTR_ERR(current->audit);
+ current->audit = NULL;
+ goto out;
+ }

/* are we setting or clearing? */
if (uid_valid(loginuid)) {
@@ -2325,8 +2474,9 @@ int audit_set_loginuid(kuid_t loginuid)
sessionid = (unsigned int)atomic_inc_return(&session_id);
}

- current->sessionid = sessionid;
- current->loginuid = loginuid;
+ info = current->audit;
+ info->sessionid = sessionid;
+ info->loginuid = loginuid;
out:
audit_log_set_loginuid(oldloginuid, loginuid, oldsessionid, sessionid, rc);
return rc;
diff --git a/kernel/audit.h b/kernel/audit.h
index 3b9c0945225a..aa81d913a3d2 100644
--- a/kernel/audit.h
+++ b/kernel/audit.h
@@ -251,6 +251,10 @@ extern void audit_put_tty(struct tty_struct *tty);
extern unsigned int audit_serial(void);
extern int auditsc_get_stamp(struct audit_context *ctx,
struct timespec64 *t, unsigned int *serial);
+extern void audit_set_context(struct task_struct *task, struct audit_context *ctx);
+extern struct audit_context *_audit_context(struct task_struct *tsk);
+extern int audit_alloc_syscall(struct task_struct *tsk);
+extern void audit_free_syscall(struct task_struct *tsk);

extern void audit_put_watch(struct audit_watch *watch);
extern void audit_get_watch(struct audit_watch *watch);
@@ -292,6 +296,9 @@ extern void audit_filter_inodes(struct task_struct *tsk,
extern struct list_head *audit_killed_trees(void);
#else /* CONFIG_AUDITSYSCALL */
#define auditsc_get_stamp(c, t, s) 0
+#define audit_alloc_syscall(t) 0
+#define audit_free_syscall(t) {}
+
#define audit_put_watch(w) {}
#define audit_get_watch(w) {}
#define audit_to_watch(k, p, l, o) (-EINVAL)
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 9cbe6d5437be..dc8dc103a8a4 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -932,23 +932,25 @@ static inline struct audit_context *audit_alloc_context(enum audit_state state)
return context;
}

-/**
- * audit_alloc - allocate an audit context block for a task
+/*
+ * audit_alloc_syscall - allocate an audit context block for a task
* @tsk: task
*
* Filter on the task information and allocate a per-task audit context
* if necessary. Doing so turns on system call auditing for the
- * specified task. This is called from copy_process, so no lock is
- * needed.
+ * specified task. This is called from copy_process via audit_alloc, so
+ * no lock is needed.
*/
-int audit_alloc(struct task_struct *tsk)
+int audit_alloc_syscall(struct task_struct *tsk)
{
struct audit_context *context;
enum audit_state state;
char *key = NULL;

- if (likely(!audit_ever_enabled))
+ if (likely(!audit_ever_enabled)) {
+ audit_set_context(tsk, NULL);
return 0; /* Return if not auditing. */
+ }

state = audit_filter_task(tsk, &key);
if (state == AUDIT_DISABLED) {
@@ -958,7 +960,7 @@ int audit_alloc(struct task_struct *tsk)

if (!(context = audit_alloc_context(state))) {
kfree(key);
- audit_log_lost("out of memory in audit_alloc");
+ audit_log_lost("out of memory in audit_alloc_syscall");
return -ENOMEM;
}
context->filterkey = key;
@@ -1603,14 +1605,14 @@ static void audit_log_exit(void)
}

/**
- * __audit_free - free a per-task audit context
+ * audit_free_syscall - free per-task audit context info
* @tsk: task whose audit context block to free
*
- * Called from copy_process and do_exit
+ * Called from audit_free
*/
-void __audit_free(struct task_struct *tsk)
+void audit_free_syscall(struct task_struct *tsk)
{
- struct audit_context *context = tsk->audit_context;
+ struct audit_context *context = _audit_context(tsk);

if (!context)
return;
diff --git a/kernel/fork.c b/kernel/fork.c
index 32083db7a2a2..261446f7bbee 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2024,7 +2024,6 @@ static __latent_entropy struct task_struct *copy_process(
posix_cputimers_init(&p->posix_cputimers);

p->io_context = NULL;
- audit_set_context(p, NULL);
cgroup_fork(p);
#ifdef CONFIG_NUMA
p->mempolicy = mpol_dup(p->mempolicy);
--
2.18.4