linux-kernel - [PATCH] lib/notifier-error-inject: fix error when writing errno to debugfs file

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Date:   Sat, 17 Sep 2022 16:06:08 +0900
From:   Akinobu Mita <akinobu.mita@...il.com>
To:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
        corbet@....net, david@...hat.com, osalvador@...e.de,
        shuah@...nel.org, Zhao Gongyi <zhaogongyi@...wei.com>
Cc:     Akinobu Mita <akinobu.mita@...il.com>,
        Wei Yongjun <weiyongjun1@...wei.com>
Subject: [PATCH] lib/notifier-error-inject: fix error when writing errno to debugfs file

The simple attribute files do not accept a negative value since the
commit 488dac0c9237 ("libfs: fix error cast of negative value in
simple_attr_write()"), so we can no longer use DEFINE_SIMPLE_ATTRIBUTE() to
define a file operations for errno value.

Fixes: 488dac0c9237 ("libfs: fix error cast of negative value in simple_attr_write()")
Reported-by: Wei Yongjun <weiyongjun1@...wei.com>
Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
---
 lib/notifier-error-inject.c | 38 ++++++++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/lib/notifier-error-inject.c b/lib/notifier-error-inject.c
index 21016b32d313..30ec41f58d53 100644
--- a/lib/notifier-error-inject.c
+++ b/lib/notifier-error-inject.c
@@ -3,20 +3,44 @@
 
 #include "notifier-error-inject.h"
 
-static int debugfs_errno_set(void *data, u64 val)
+static int notifier_err_errno_show(struct seq_file *m, void *data)
 {
-	*(int *)data = clamp_t(int, val, -MAX_ERRNO, 0);
+	int *value = m->private;
+
+	seq_printf(m, "%d\n", *value);
+
 	return 0;
 }
 
-static int debugfs_errno_get(void *data, u64 *val)
+static int notifier_err_errno_open(struct inode *inode, struct file *file)
 {
-	*val = *(int *)data;
-	return 0;
+	return single_open(file, notifier_err_errno_show, inode->i_private);
+}
+
+static ssize_t notifier_err_errno_write(struct file *file, const char __user *ubuf, size_t len,
+					loff_t *offp)
+{
+	struct seq_file *m = file->private_data;
+	int *value = m->private;
+	int ret;
+
+	ret = kstrtoint_from_user(ubuf, len, 0, value);
+	if (ret)
+		return ret;
+
+	*value = clamp(*value, -MAX_ERRNO, 0);
+
+	return len;
 }
 
-DEFINE_SIMPLE_ATTRIBUTE(fops_errno, debugfs_errno_get, debugfs_errno_set,
-			"%lld\n");
+static const struct file_operations fops_errno = {
+	.owner = THIS_MODULE,
+	.open = notifier_err_errno_open,
+	.read = seq_read,
+	.write = notifier_err_errno_write,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
 
 static struct dentry *debugfs_create_errno(const char *name, umode_t mode,
 				struct dentry *parent, int *value)
-- 
2.34.1