Revert "exec: Transform exec_update_mutex into a rw_semaphore"

This reverts commit 117433236a which is
commit f7cfd871ae0c5008d94b6f66834e7845caa93c15 upstream.

It breaks the API and we don't need it right now in the 5.4 tree.

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ia4d89b6dfbb92d6bd48b36b1f85559a8dfb331c6

fs/exec.c

@@ -1009,8 +1009,8 @@ EXPORT_SYMBOL(read_code);
 
 /*
  * Maps the mm_struct mm into the current task struct.
- * On success, this function returns with exec_update_lock
- * held for writing.
+ * On success, this function returns with the mutex
+ * exec_update_mutex locked.
  */
 static int exec_mmap(struct mm_struct *mm)
 {
@@ -1023,7 +1023,7 @@ static int exec_mmap(struct mm_struct *mm)
 	old_mm = current->mm;
 	exec_mm_release(tsk, old_mm);
 
-	ret = down_write_killable(&tsk->signal->exec_update_lock);
+	ret = mutex_lock_killable(&tsk->signal->exec_update_mutex);
 	if (ret)
 		return ret;
 
@@ -1038,7 +1038,7 @@ static int exec_mmap(struct mm_struct *mm)
 		down_read(&old_mm->mmap_sem);
 		if (unlikely(old_mm->core_state)) {
 			up_read(&old_mm->mmap_sem);
-			up_write(&tsk->signal->exec_update_lock);
+			mutex_unlock(&tsk->signal->exec_update_mutex);
 			return -EINTR;
 		}
 	}
@@ -1450,7 +1450,7 @@ static void free_bprm(struct linux_binprm *bprm)
 	free_arg_pages(bprm);
 	if (bprm->cred) {
 		if (bprm->called_exec_mmap)
-			up_write(&current->signal->exec_update_lock);
+			mutex_unlock(&current->signal->exec_update_mutex);
 		mutex_unlock(&current->signal->cred_guard_mutex);
 		abort_creds(bprm->cred);
 	}
@@ -1500,7 +1500,7 @@ void install_exec_creds(struct linux_binprm *bprm)
 	 * credentials; any time after this it may be unlocked.
 	 */
 	security_bprm_committed_creds(bprm);
-	up_write(&current->signal->exec_update_lock);
+	mutex_unlock(&current->signal->exec_update_mutex);
 	mutex_unlock(&current->signal->cred_guard_mutex);
 }
 EXPORT_SYMBOL(install_exec_creds);

fs/proc/base.c

@@ -404,11 +404,11 @@ print0:
 
 static int lock_trace(struct task_struct *task)
 {
-	int err = down_read_killable(&task->signal->exec_update_lock);
+	int err = mutex_lock_killable(&task->signal->exec_update_mutex);
 	if (err)
 		return err;
 	if (!ptrace_may_access(task, PTRACE_MODE_ATTACH_FSCREDS)) {
-		up_read(&task->signal->exec_update_lock);
+		mutex_unlock(&task->signal->exec_update_mutex);
 		return -EPERM;
 	}
 	return 0;
@@ -416,7 +416,7 @@ static int lock_trace(struct task_struct *task)
 
 static void unlock_trace(struct task_struct *task)
 {
-	up_read(&task->signal->exec_update_lock);
+	mutex_unlock(&task->signal->exec_update_mutex);
 }
 
 #ifdef CONFIG_STACKTRACE
@@ -2770,7 +2770,7 @@ static int do_io_accounting(struct task_struct *task, struct seq_file *m, int wh
 	unsigned long flags;
 	int result;
 
-	result = down_read_killable(&task->signal->exec_update_lock);
+	result = mutex_lock_killable(&task->signal->exec_update_mutex);
 	if (result)
 		return result;
 
@@ -2806,7 +2806,7 @@ static int do_io_accounting(struct task_struct *task, struct seq_file *m, int wh
 	result = 0;
 
 out_unlock:
-	up_read(&task->signal->exec_update_lock);
+	mutex_unlock(&task->signal->exec_update_mutex);
 	return result;
 }
 

include/linux/sched/signal.h

@@ -227,13 +227,12 @@ struct signal_struct {
 					 * credential calculations
 					 * (notably. ptrace)
 					 * Deprecated do not use in new code.
-					 * Use exec_update_lock instead.
+					 * Use exec_update_mutex instead.
+					 */
+	struct mutex exec_update_mutex;	/* Held while task_struct is being
+					 * updated during exec, and may have
+					 * inconsistent permissions.
 					 */
-	struct rw_semaphore exec_update_lock;	/* Held while task_struct is
-						 * being updated during exec,
-						 * and may have inconsistent
-						 * permissions.
-						 */
 	ANDROID_KABI_RESERVE(1);
 	ANDROID_KABI_RESERVE(2);
 	ANDROID_KABI_RESERVE(3);

init/init_task.c

@@ -27,7 +27,7 @@ static struct signal_struct init_signals = {
 	.multiprocess	= HLIST_HEAD_INIT,
 	.rlim		= INIT_RLIMITS,
 	.cred_guard_mutex = __MUTEX_INITIALIZER(init_signals.cred_guard_mutex),
-	.exec_update_lock = __RWSEM_INITIALIZER(init_signals.exec_update_lock),
+	.exec_update_mutex = __MUTEX_INITIALIZER(init_signals.exec_update_mutex),
 #ifdef CONFIG_POSIX_TIMERS
 	.posix_timers = LIST_HEAD_INIT(init_signals.posix_timers),
 	.cputimer	= {

kernel/events/core.c

@@ -1254,7 +1254,7 @@ static void put_ctx(struct perf_event_context *ctx)
  * function.
  *
  * Lock order:
- *    exec_update_lock
+ *    exec_update_mutex
  *	task_struct::perf_event_mutex
  *	  perf_event_context::mutex
  *	    perf_event::child_mutex;
@@ -11163,14 +11163,14 @@ SYSCALL_DEFINE5(perf_event_open,
 	}
 
 	if (task) {
-		err = down_read_interruptible(&task->signal->exec_update_lock);
+		err = mutex_lock_interruptible(&task->signal->exec_update_mutex);
 		if (err)
 			goto err_file;
 
 		/*
 		 * Preserve ptrace permission check for backwards compatibility.
 		 *
-		 * We must hold exec_update_lock across this and any potential
+		 * We must hold exec_update_mutex across this and any potential
 		 * perf_install_in_context() call for this new event to
 		 * serialize against exec() altering our credentials (and the
 		 * perf_event_exit_task() that could imply).
@@ -11333,7 +11333,7 @@ SYSCALL_DEFINE5(perf_event_open,
 	mutex_unlock(&ctx->mutex);
 
 	if (task) {
-		up_read(&task->signal->exec_update_lock);
+		mutex_unlock(&task->signal->exec_update_mutex);
 		put_task_struct(task);
 	}
 
@@ -11357,7 +11357,7 @@ err_locked:
 	mutex_unlock(&ctx->mutex);
 err_cred:
 	if (task)
-		up_read(&task->signal->exec_update_lock);
+		mutex_unlock(&task->signal->exec_update_mutex);
 err_file:
 	fput(event_file);
 err_context:
@@ -11674,7 +11674,7 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn)
 /*
  * When a child task exits, feed back event values to parent events.
  *
- * Can be called with exec_update_lock held when called from
+ * Can be called with exec_update_mutex held when called from
  * install_exec_creds().
  */
 void perf_event_exit_task(struct task_struct *child)

kernel/fork.c

@@ -1232,7 +1232,7 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
 	struct mm_struct *mm;
 	int err;
 
-	err =  down_read_killable(&task->signal->exec_update_lock);
+	err =  mutex_lock_killable(&task->signal->exec_update_mutex);
 	if (err)
 		return ERR_PTR(err);
 
@@ -1242,7 +1242,7 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
 		mmput(mm);
 		mm = ERR_PTR(-EACCES);
 	}
-	up_read(&task->signal->exec_update_lock);
+	mutex_unlock(&task->signal->exec_update_mutex);
 
 	return mm;
 }
@@ -1597,7 +1597,7 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 	sig->oom_score_adj_min = current->signal->oom_score_adj_min;
 
 	mutex_init(&sig->cred_guard_mutex);
-	init_rwsem(&sig->exec_update_lock);
+	mutex_init(&sig->exec_update_mutex);
 
 	return 0;
 }

kernel/kcmp.c

@@ -75,25 +75,25 @@ get_file_raw_ptr(struct task_struct *task, unsigned int idx)
 	return file;
 }
 
-static void kcmp_unlock(struct rw_semaphore *l1, struct rw_semaphore *l2)
+static void kcmp_unlock(struct mutex *m1, struct mutex *m2)
 {
-	if (likely(l2 != l1))
-		up_read(l2);
-	up_read(l1);
+	if (likely(m2 != m1))
+		mutex_unlock(m2);
+	mutex_unlock(m1);
 }
 
-static int kcmp_lock(struct rw_semaphore *l1, struct rw_semaphore *l2)
+static int kcmp_lock(struct mutex *m1, struct mutex *m2)
 {
 	int err;
 
-	if (l2 > l1)
-		swap(l1, l2);
+	if (m2 > m1)
+		swap(m1, m2);
 
-	err = down_read_killable(l1);
-	if (!err && likely(l1 != l2)) {
-		err = down_read_killable_nested(l2, SINGLE_DEPTH_NESTING);
+	err = mutex_lock_killable(m1);
+	if (!err && likely(m1 != m2)) {
+		err = mutex_lock_killable_nested(m2, SINGLE_DEPTH_NESTING);
 		if (err)
-			up_read(l1);
+			mutex_unlock(m1);
 	}
 
 	return err;
@@ -173,8 +173,8 @@ SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type,
 	/*
 	 * One should have enough rights to inspect task details.
 	 */
-	ret = kcmp_lock(&task1->signal->exec_update_lock,
-			&task2->signal->exec_update_lock);
+	ret = kcmp_lock(&task1->signal->exec_update_mutex,
+			&task2->signal->exec_update_mutex);
 	if (ret)
 		goto err;
 	if (!ptrace_may_access(task1, PTRACE_MODE_READ_REALCREDS) ||
@@ -229,8 +229,8 @@ SYSCALL_DEFINE5(kcmp, pid_t, pid1, pid_t, pid2, int, type,
 	}
 
 err_unlock:
-	kcmp_unlock(&task1->signal->exec_update_lock,
-		    &task2->signal->exec_update_lock);
+	kcmp_unlock(&task1->signal->exec_update_mutex,
+		    &task2->signal->exec_update_mutex);
 err:
 	put_task_struct(task1);
 	put_task_struct(task2);

kernel/locking/rwsem.c

@@ -1538,7 +1538,7 @@ int __sched down_read_interruptible(struct rw_semaphore *sem)
 	rwsem_acquire_read(&sem->dep_map, 0, 0, _RET_IP_);
 
 	if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_interruptible)) {
-		rwsem_release(&sem->dep_map, 1, _RET_IP_);
+		rwsem_release(&sem->dep_map, _RET_IP_);
 		return -EINTR;
 	}
 
@@ -1664,7 +1664,7 @@ int down_read_killable_nested(struct rw_semaphore *sem, int subclass)
 	rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
 
 	if (LOCK_CONTENDED_RETURN(sem, __down_read_trylock, __down_read_killable)) {
-		rwsem_release(&sem->dep_map, 1, _RET_IP_);
+		rwsem_release(&sem->dep_map, _RET_IP_);
 		return -EINTR;
 	}