[PATCH RFC 07/23] s390/dasd: let procfs copy in writes to /proc/dasd/statistics

[Christian Brauner]

Implement ->proc_write_buf() so procfs copies in what is written before
it pins the entry, and parse the command from that copy. Commands longer
than PAGE_SIZE - 1 bytes are rejected now instead of cut at 64k.

Signed-off-by: Christian Brauner (Amutable) <brauner@xxxxxxxxxx>
---
 drivers/s390/block/dasd_proc.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/drivers/s390/block/dasd_proc.c b/drivers/s390/block/dasd_proc.c
index 86399427f01d..6c3bbb7dfe85 100644
--- a/drivers/s390/block/dasd_proc.c
+++ b/drivers/s390/block/dasd_proc.c
@@ -15,7 +15,6 @@
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/seq_file.h>
-#include <linux/vmalloc.h>
 #include <linux/proc_fs.h>
 
 #include <asm/debug.h>
@@ -247,17 +246,15 @@ static int dasd_stats_proc_show(struct seq_file *m, void *v)
 }
 
 static ssize_t dasd_stats_proc_write(struct file *file,
-		const char __user *user_buf, size_t user_len, loff_t *pos)
+		char *buffer, size_t user_len, loff_t *pos)
 {
 #ifdef CONFIG_DASD_PROFILE
-	char *buffer, *str;
+	char *str;
 	int rc;
 
-	if (user_len > 65536)
-		user_len = 65536;
-	buffer = dasd_get_user_string(user_buf, user_len);
-	if (IS_ERR(buffer))
-		return PTR_ERR(buffer);
+	/* strip linefeed */
+	if (user_len && buffer[user_len - 1] == '\n')
+		buffer[user_len - 1] = 0;
 
 	/* check for valid verbs */
 	str = skip_spaces(buffer);
@@ -296,13 +293,11 @@ static ssize_t dasd_stats_proc_write(struct file *file,
 		pr_info("The statistics have been reset\n");
 	} else
 		goto out_parse_error;
-	vfree(buffer);
 	return user_len;
 out_parse_error:
 	rc = -EINVAL;
 	pr_warn("%s is not a supported value for /proc/dasd/statistics\n", str);
 out_error:
-	vfree(buffer);
 	return rc;
 #else
 	pr_warn("/proc/dasd/statistics: is not activated in this kernel\n");
@@ -312,7 +307,7 @@ out_error:
 
 static const struct proc_ops dasd_stats_proc_ops = {
 	.proc_show	= dasd_stats_proc_show,
-	.proc_write	= dasd_stats_proc_write,
+	.proc_write_buf	= dasd_stats_proc_write,
 };
 
 /*

-- 
2.53.0