Update Linux to v5.4.148

Sourced from [1]

[1] https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.4.148.tar.gz

Change-Id: Ib3d26c5ba9b022e2e03533005c4fed4d7c30b61b
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/fs/proc/base.c b/fs/proc/base.c
index ebea950..5a187e9 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -403,11 +403,11 @@
 
 static int lock_trace(struct task_struct *task)
 {
-	int err = mutex_lock_killable(&task->signal->cred_guard_mutex);
+	int err = down_read_killable(&task->signal->exec_update_lock);
 	if (err)
 		return err;
 	if (!ptrace_may_access(task, PTRACE_MODE_ATTACH_FSCREDS)) {
-		mutex_unlock(&task->signal->cred_guard_mutex);
+		up_read(&task->signal->exec_update_lock);
 		return -EPERM;
 	}
 	return 0;
@@ -415,7 +415,7 @@
 
 static void unlock_trace(struct task_struct *task)
 {
-	mutex_unlock(&task->signal->cred_guard_mutex);
+	up_read(&task->signal->exec_update_lock);
 }
 
 #ifdef CONFIG_STACKTRACE
@@ -549,8 +549,17 @@
 {
 	unsigned long totalpages = totalram_pages() + total_swap_pages;
 	unsigned long points = 0;
+	long badness;
 
-	points = oom_badness(task, totalpages) * 1000 / totalpages;
+	badness = oom_badness(task, totalpages);
+	/*
+	 * Special case OOM_SCORE_ADJ_MIN for all others scale the
+	 * badness value into [0, 2000] range which we have been
+	 * exporting for a long time so userspace might depend on it.
+	 */
+	if (badness != LONG_MIN)
+		points = (1000 + badness * 1000 / (long)totalpages) * 2 / 3;
+
 	seq_printf(m, "%lu\n", points);
 
 	return 0;
@@ -836,7 +845,7 @@
 	flags = FOLL_FORCE | (write ? FOLL_WRITE : 0);
 
 	while (count > 0) {
-		int this_len = min_t(int, count, PAGE_SIZE);
+		size_t this_len = min_t(size_t, count, PAGE_SIZE);
 
 		if (write && copy_from_user(page, buf, this_len)) {
 			copied = -EFAULT;
@@ -1036,7 +1045,6 @@
 
 static int __set_oom_adj(struct file *file, int oom_adj, bool legacy)
 {
-	static DEFINE_MUTEX(oom_adj_mutex);
 	struct mm_struct *mm = NULL;
 	struct task_struct *task;
 	int err = 0;
@@ -1076,7 +1084,7 @@
 		struct task_struct *p = find_lock_task_mm(task);
 
 		if (p) {
-			if (atomic_read(&p->mm->mm_users) > 1) {
+			if (test_bit(MMF_MULTIPROCESS, &p->mm->flags)) {
 				mm = p->mm;
 				mmgrab(mm);
 			}
@@ -2528,6 +2536,13 @@
 }
 
 #ifdef CONFIG_SECURITY
+static int proc_pid_attr_open(struct inode *inode, struct file *file)
+{
+	file->private_data = NULL;
+	__mem_open(inode, file, PTRACE_MODE_READ_FSCREDS);
+	return 0;
+}
+
 static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
 				  size_t count, loff_t *ppos)
 {
@@ -2557,6 +2572,10 @@
 	void *page;
 	int rv;
 
+	/* A task may only write when it was the opener. */
+	if (file->private_data != current->mm)
+		return -EPERM;
+
 	rcu_read_lock();
 	task = pid_task(proc_pid(inode), PIDTYPE_PID);
 	if (!task) {
@@ -2604,9 +2623,11 @@
 }
 
 static const struct file_operations proc_pid_attr_operations = {
+	.open		= proc_pid_attr_open,
 	.read		= proc_pid_attr_read,
 	.write		= proc_pid_attr_write,
 	.llseek		= generic_file_llseek,
+	.release	= mem_release,
 };
 
 #define LSM_DIR_OPS(LSM) \
@@ -2770,7 +2791,7 @@
 	unsigned long flags;
 	int result;
 
-	result = mutex_lock_killable(&task->signal->cred_guard_mutex);
+	result = down_read_killable(&task->signal->exec_update_lock);
 	if (result)
 		return result;
 
@@ -2806,7 +2827,7 @@
 	result = 0;
 
 out_unlock:
-	mutex_unlock(&task->signal->cred_guard_mutex);
+	up_read(&task->signal->exec_update_lock);
 	return result;
 }