cred: get rid of CONFIG_DEBUG_CREDENTIALS

This code is rarely (never?) enabled by distros, and it hasn't caught
anything in decades. Let's kill off this legacy debug code.

Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 16 insertions, 218 deletions

diff --git a/kernel/cred.c b/kernel/cred.c
index 4a6cd0f0fef5..c033a201c808 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -43,10 +43,6 @@ static struct group_info init_groups = { .usage = REFCOUNT_INIT(2) };
  */
 struct cred init_cred = {
 	.usage			= ATOMIC_INIT(4),
-#ifdef CONFIG_DEBUG_CREDENTIALS
-	.subscribers		= ATOMIC_INIT(2),
-	.magic			= CRED_MAGIC,
-#endif
 	.uid			= GLOBAL_ROOT_UID,
 	.gid			= GLOBAL_ROOT_GID,
 	.suid			= GLOBAL_ROOT_UID,
@@ -66,31 +62,6 @@ struct cred init_cred = {
 	.ucounts		= &init_ucounts,
 };
 
-static inline void set_cred_subscribers(struct cred *cred, int n)
-{
-#ifdef CONFIG_DEBUG_CREDENTIALS
-	atomic_set(&cred->subscribers, n);
-#endif
-}
-
-static inline int read_cred_subscribers(const struct cred *cred)
-{
-#ifdef CONFIG_DEBUG_CREDENTIALS
-	return atomic_read(&cred->subscribers);
-#else
-	return 0;
-#endif
-}
-
-static inline void alter_cred_subscribers(const struct cred *_cred, int n)
-{
-#ifdef CONFIG_DEBUG_CREDENTIALS
-	struct cred *cred = (struct cred *) _cred;
-
-	atomic_add(n, &cred->subscribers);
-#endif
-}
-
 /*
  * The RCU callback to actually dispose of a set of credentials
  */
@@ -100,20 +71,9 @@ static void put_cred_rcu(struct rcu_head *rcu)
 
 	kdebug("put_cred_rcu(%p)", cred);
 
-#ifdef CONFIG_DEBUG_CREDENTIALS
-	if (cred->magic != CRED_MAGIC_DEAD ||
-	    atomic_long_read(&cred->usage) != 0 ||
-	    read_cred_subscribers(cred) != 0)
-		panic("CRED: put_cred_rcu() sees %p with"
-		      " mag %x, put %p, usage %ld, subscr %d\n",
-		      cred, cred->magic, cred->put_addr,
-		      atomic_long_read(&cred->usage),
-		      read_cred_subscribers(cred));
-#else
 	if (atomic_long_read(&cred->usage) != 0)
 		panic("CRED: put_cred_rcu() sees %p with usage %ld\n",
 		      cred, atomic_long_read(&cred->usage));
-#endif
 
 	security_cred_free(cred);
 	key_put(cred->session_keyring);
@@ -137,16 +97,10 @@ static void put_cred_rcu(struct rcu_head *rcu)
  */
 void __put_cred(struct cred *cred)
 {
-	kdebug("__put_cred(%p{%ld,%d})", cred,
-	       atomic_long_read(&cred->usage),
-	       read_cred_subscribers(cred));
+	kdebug("__put_cred(%p{%ld})", cred,
+	       atomic_long_read(&cred->usage));
 
 	BUG_ON(atomic_long_read(&cred->usage) != 0);
-#ifdef CONFIG_DEBUG_CREDENTIALS
-	BUG_ON(read_cred_subscribers(cred) != 0);
-	cred->magic = CRED_MAGIC_DEAD;
-	cred->put_addr = __builtin_return_address(0);
-#endif
 	BUG_ON(cred == current->cred);
 	BUG_ON(cred == current->real_cred);
 
@@ -164,9 +118,8 @@ void exit_creds(struct task_struct *tsk)
 {
 	struct cred *real_cred, *cred;
 
-	kdebug("exit_creds(%u,%p,%p,{%ld,%d})", tsk->pid, tsk->real_cred, tsk->cred,
-	       atomic_long_read(&tsk->cred->usage),
-	       read_cred_subscribers(tsk->cred));
+	kdebug("exit_creds(%u,%p,%p,{%ld})", tsk->pid, tsk->real_cred, tsk->cred,
+	       atomic_long_read(&tsk->cred->usage));
 
 	real_cred = (struct cred *) tsk->real_cred;
 	tsk->real_cred = NULL;
@@ -174,15 +127,10 @@ void exit_creds(struct task_struct *tsk)
 	cred = (struct cred *) tsk->cred;
 	tsk->cred = NULL;
 
-	validate_creds(cred);
 	if (real_cred == cred) {
-		alter_cred_subscribers(cred, -2);
 		put_cred_many(cred, 2);
 	} else {
-		validate_creds(real_cred);
-		alter_cred_subscribers(real_cred, -1);
 		put_cred(real_cred);
-		alter_cred_subscribers(cred, -1);
 		put_cred(cred);
 	}
 
@@ -231,9 +179,6 @@ struct cred *cred_alloc_blank(void)
 		return NULL;
 
 	atomic_long_set(&new->usage, 1);
-#ifdef CONFIG_DEBUG_CREDENTIALS
-	new->magic = CRED_MAGIC;
-#endif
 	if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)
 		goto error;
 
@@ -264,8 +209,6 @@ struct cred *prepare_creds(void)
 	const struct cred *old;
 	struct cred *new;
 
-	validate_process_creds();
-
 	new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
 	if (!new)
 		return NULL;
@@ -277,7 +220,6 @@ struct cred *prepare_creds(void)
 
 	new->non_rcu = 0;
 	atomic_long_set(&new->usage, 1);
-	set_cred_subscribers(new, 0);
 	get_group_info(new->group_info);
 	get_uid(new->user);
 	get_user_ns(new->user_ns);
@@ -300,7 +242,6 @@ struct cred *prepare_creds(void)
 	if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)
 		goto error;
 
-	validate_creds(new);
 	return new;
 
 error:
@@ -362,10 +303,8 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags)
 		clone_flags & CLONE_THREAD
 	    ) {
 		p->real_cred = get_cred_many(p->cred, 2);
-		alter_cred_subscribers(p->cred, 2);
-		kdebug("share_creds(%p{%ld,%d})",
-		       p->cred, atomic_long_read(&p->cred->usage),
-		       read_cred_subscribers(p->cred));
+		kdebug("share_creds(%p{%ld})",
+		       p->cred, atomic_long_read(&p->cred->usage));
 		inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
 		return 0;
 	}
@@ -404,8 +343,6 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags)
 
 	p->cred = p->real_cred = get_cred(new);
 	inc_rlimit_ucounts(task_ucounts(p), UCOUNT_RLIMIT_NPROC, 1);
-	alter_cred_subscribers(new, 2);
-	validate_creds(new);
 	return 0;
 
 error_put:
@@ -457,16 +394,10 @@ int commit_creds(struct cred *new)
 	struct task_struct *task = current;
 	const struct cred *old = task->real_cred;
 
-	kdebug("commit_creds(%p{%ld,%d})", new,
-	       atomic_long_read(&new->usage),
-	       read_cred_subscribers(new));
+	kdebug("commit_creds(%p{%ld})", new,
+	       atomic_long_read(&new->usage));
 
 	BUG_ON(task->cred != old);
-#ifdef CONFIG_DEBUG_CREDENTIALS
-	BUG_ON(read_cred_subscribers(old) < 2);
-	validate_creds(old);
-	validate_creds(new);
-#endif
 	BUG_ON(atomic_long_read(&new->usage) < 1);
 
 	get_cred(new); /* we will require a ref for the subj creds too */
@@ -502,14 +433,12 @@ int commit_creds(struct cred *new)
 	 * RLIMIT_NPROC limits on user->processes have already been checked
 	 * in set_user().
 	 */
-	alter_cred_subscribers(new, 2);
 	if (new->user != old->user || new->user_ns != old->user_ns)
 		inc_rlimit_ucounts(new->ucounts, UCOUNT_RLIMIT_NPROC, 1);
 	rcu_assign_pointer(task->real_cred, new);
 	rcu_assign_pointer(task->cred, new);
 	if (new->user != old->user || new->user_ns != old->user_ns)
 		dec_rlimit_ucounts(old->ucounts, UCOUNT_RLIMIT_NPROC, 1);
-	alter_cred_subscribers(old, -2);
 
 	/* send notifications */
 	if (!uid_eq(new->uid,   old->uid)  ||
@@ -539,13 +468,9 @@ EXPORT_SYMBOL(commit_creds);
  */
 void abort_creds(struct cred *new)
 {
-	kdebug("abort_creds(%p{%ld,%d})", new,
-	       atomic_long_read(&new->usage),
-	       read_cred_subscribers(new));
+	kdebug("abort_creds(%p{%ld})", new,
+	       atomic_long_read(&new->usage));
 
-#ifdef CONFIG_DEBUG_CREDENTIALS
-	BUG_ON(read_cred_subscribers(new) != 0);
-#endif
 	BUG_ON(atomic_long_read(&new->usage) < 1);
 	put_cred(new);
 }
@@ -562,12 +487,8 @@ const struct cred *override_creds(const struct cred *new)
 {
 	const struct cred *old = current->cred;
 
-	kdebug("override_creds(%p{%ld,%d})", new,
-	       atomic_long_read(&new->usage),
-	       read_cred_subscribers(new));
-
-	validate_creds(old);
-	validate_creds(new);
+	kdebug("override_creds(%p{%ld})", new,
+	       atomic_long_read(&new->usage));
 
 	/*
 	 * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
@@ -576,18 +497,12 @@ const struct cred *override_creds(const struct cred *new)
 	 * we are only installing the cred into the thread-synchronous
 	 * '->cred' pointer, not the '->real_cred' pointer that is
 	 * visible to other threads under RCU.
-	 *
-	 * Also note that we did validate_creds() manually, not depending
-	 * on the validation in 'get_cred()'.
 	 */
 	get_new_cred((struct cred *)new);
-	alter_cred_subscribers(new, 1);
 	rcu_assign_pointer(current->cred, new);
-	alter_cred_subscribers(old, -1);
 
-	kdebug("override_creds() = %p{%ld,%d}", old,
-	       atomic_long_read(&old->usage),
-	       read_cred_subscribers(old));
+	kdebug("override_creds() = %p{%ld}", old,
+	       atomic_long_read(&old->usage));
 	return old;
 }
 EXPORT_SYMBOL(override_creds);
@@ -603,15 +518,10 @@ void revert_creds(const struct cred *old)
 {
 	const struct cred *override = current->cred;
 
-	kdebug("revert_creds(%p{%ld,%d})", old,
-	       atomic_long_read(&old->usage),
-	       read_cred_subscribers(old));
+	kdebug("revert_creds(%p{%ld})", old,
+	       atomic_long_read(&old->usage));
 
-	validate_creds(old);
-	validate_creds(override);
-	alter_cred_subscribers(old, 1);
 	rcu_assign_pointer(current->cred, old);
-	alter_cred_subscribers(override, -1);
 	put_cred(override);
 }
 EXPORT_SYMBOL(revert_creds);
@@ -731,12 +641,10 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
 	kdebug("prepare_kernel_cred() alloc %p", new);
 
 	old = get_task_cred(daemon);
-	validate_creds(old);
 
 	*new = *old;
 	new->non_rcu = 0;
 	atomic_long_set(&new->usage, 1);
-	set_cred_subscribers(new, 0);
 	get_uid(new->user);
 	get_user_ns(new->user_ns);
 	get_group_info(new->group_info);
@@ -760,7 +668,6 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
 		goto error;
 
 	put_cred(old);
-	validate_creds(new);
 	return new;
 
 error:
@@ -825,109 +732,3 @@ int set_create_files_as(struct cred *new, struct inode *inode)
 	return security_kernel_create_files_as(new, inode);
 }
 EXPORT_SYMBOL(set_create_files_as);
-
-#ifdef CONFIG_DEBUG_CREDENTIALS
-
-bool creds_are_invalid(const struct cred *cred)
-{
-	if (cred->magic != CRED_MAGIC)
-		return true;
-	return false;
-}
-EXPORT_SYMBOL(creds_are_invalid);
-
-/*
- * dump invalid credentials
- */
-static void dump_invalid_creds(const struct cred *cred, const char *label,
-			       const struct task_struct *tsk)
-{
-	pr_err("%s credentials: %p %s%s%s\n",
-	       label, cred,
-	       cred == &init_cred ? "[init]" : "",
-	       cred == tsk->real_cred ? "[real]" : "",
-	       cred == tsk->cred ? "[eff]" : "");
-	pr_err("->magic=%x, put_addr=%p\n",
-	       cred->magic, cred->put_addr);
-	pr_err("->usage=%ld, subscr=%d\n",
-	       atomic_long_read(&cred->usage),
-	       read_cred_subscribers(cred));
-	pr_err("->*uid = { %d,%d,%d,%d }\n",
-		from_kuid_munged(&init_user_ns, cred->uid),
-		from_kuid_munged(&init_user_ns, cred->euid),
-		from_kuid_munged(&init_user_ns, cred->suid),
-		from_kuid_munged(&init_user_ns, cred->fsuid));
-	pr_err("->*gid = { %d,%d,%d,%d }\n",
-		from_kgid_munged(&init_user_ns, cred->gid),
-		from_kgid_munged(&init_user_ns, cred->egid),
-		from_kgid_munged(&init_user_ns, cred->sgid),
-		from_kgid_munged(&init_user_ns, cred->fsgid));
-#ifdef CONFIG_SECURITY
-	pr_err("->security is %p\n", cred->security);
-	if ((unsigned long) cred->security >= PAGE_SIZE &&
-	    (((unsigned long) cred->security & 0xffffff00) !=
-	     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
-		pr_err("->security {%x, %x}\n",
-		       ((u32*)cred->security)[0],
-		       ((u32*)cred->security)[1]);
-#endif
-}
-
-/*
- * report use of invalid credentials
- */
-void __noreturn __invalid_creds(const struct cred *cred, const char *file, unsigned line)
-{
-	pr_err("Invalid credentials\n");
-	pr_err("At %s:%u\n", file, line);
-	dump_invalid_creds(cred, "Specified", current);
-	BUG();
-}
-EXPORT_SYMBOL(__invalid_creds);
-
-/*
- * check the credentials on a process
- */
-void __validate_process_creds(struct task_struct *tsk,
-			      const char *file, unsigned line)
-{
-	if (tsk->cred == tsk->real_cred) {
-		if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
-			     creds_are_invalid(tsk->cred)))
-			goto invalid_creds;
-	} else {
-		if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
-			     read_cred_subscribers(tsk->cred) < 1 ||
-			     creds_are_invalid(tsk->real_cred) ||
-			     creds_are_invalid(tsk->cred)))
-			goto invalid_creds;
-	}
-	return;
-
-invalid_creds:
-	pr_err("Invalid process credentials\n");
-	pr_err("At %s:%u\n", file, line);
-
-	dump_invalid_creds(tsk->real_cred, "Real", tsk);
-	if (tsk->cred != tsk->real_cred)
-		dump_invalid_creds(tsk->cred, "Effective", tsk);
-	else
-		pr_err("Effective creds == Real creds\n");
-	BUG();
-}
-EXPORT_SYMBOL(__validate_process_creds);
-
-/*
- * check creds for do_exit()
- */
-void validate_creds_for_do_exit(struct task_struct *tsk)
-{
-	kdebug("validate_creds_for_do_exit(%p,%p{%ld,%d})",
-	       tsk->real_cred, tsk->cred,
-	       atomic_long_read(&tsk->cred->usage),
-	       read_cred_subscribers(tsk->cred));
-
-	__validate_process_creds(tsk, __FILE__, __LINE__);
-}
-
-#endif /* CONFIG_DEBUG_CREDENTIALS */
diff --git a/kernel/exit.c b/kernel/exit.c
index ee9f43bed49a..aedc0832c9f4 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -824,8 +824,6 @@ void __noreturn do_exit(long code)
 	ptrace_event(PTRACE_EVENT_EXIT, code);
 	user_events_exit(tsk);
 
-	validate_creds_for_do_exit(tsk);
-
 	io_uring_files_cancel();
 	exit_signals(tsk);  /* sets PF_EXITING */
 
@@ -909,7 +907,6 @@ void __noreturn do_exit(long code)
 	if (tsk->task_frag.page)
 		put_page(tsk->task_frag.page);
 
-	validate_creds_for_do_exit(tsk);
 	exit_task_stack_account(tsk);
 
 	check_stack_usage();