[PATCH RESEND v2 13/30] locking/lockdep: let procfs copy in writes to /proc/lock_stat

[Christian Brauner]

Implement ->proc_write_buf() so procfs copies in what is written before
it pins the entry, and look at the first character of that copy. Writes
larger than PAGE_SIZE - 1 bytes fail with -EINVAL now.

Signed-off-by: Christian Brauner (Amutable) <brauner at kernel.org>
---
 kernel/locking/lockdep_proc.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c
index 9b034b5b94bd..2a66ea09c2aa 100644
--- a/kernel/locking/lockdep_proc.c
+++ b/kernel/locking/lockdep_proc.c
@@ -669,18 +669,14 @@ static int lock_stat_open(struct inode *inode, struct file *file)
 	return 0;
 }
 
-static ssize_t lock_stat_write(struct file *file, const char __user *buf,
-			       size_t count, loff_t *ppos)
+static ssize_t lock_stat_write(struct file *file, char *buf, size_t count,
+			       loff_t *ppos)
 {
 	struct lock_class *class;
 	unsigned long idx;
-	char c;
 
 	if (count) {
-		if (get_user(c, buf))
-			return -EFAULT;
-
-		if (c != '0')
+		if (buf[0] != '0')
 			return count;
 
 		iterate_lock_classes(idx, class) {
@@ -703,7 +699,7 @@ static int lock_stat_release(struct inode *inode, struct file *file)
 static const struct proc_ops lock_stat_proc_ops = {
 	.proc_seq_ops	= &lockstat_ops,
 	.proc_open	= lock_stat_open,
-	.proc_write	= lock_stat_write,
+	.proc_write_buf	= lock_stat_write,
 	.proc_release	= lock_stat_release,
 };
 #endif /* CONFIG_LOCK_STAT */

-- 
2.53.0