1 files changed, 9 insertions, 2 deletions

diff --git a/drivers/oprofile/oprofilefs.c b/drivers/oprofile/oprofilefs.c
index d0de6cc2d7a5..2f0aa0f700e6 100644
--- a/drivers/oprofile/oprofilefs.c
+++ b/drivers/oprofile/oprofilefs.c
@@ -60,6 +60,13 @@ ssize_t oprofilefs_ulong_to_user(unsigned long val, char __user *buf, size_t cou
 }
 
 
+/*
+ * Note: If oprofilefs_ulong_from_user() returns 0, then *val remains
+ * unchanged and might be uninitialized. This follows write syscall
+ * implementation when count is zero: "If count is zero ... [and if]
+ * no errors are detected, 0 will be returned without causing any
+ * other effect." (man 2 write)
+ */
 int oprofilefs_ulong_from_user(unsigned long *val, char const __user *buf, size_t count)
 {
         char tmpbuf[TMPBUFSIZE];
@@ -79,7 +86,7 @@ int oprofilefs_ulong_from_user(unsigned long *val, char const __user *buf, size_
         raw_spin_lock_irqsave(&oprofilefs_lock, flags);
         *val = simple_strtoul(tmpbuf, NULL, 0);
         raw_spin_unlock_irqrestore(&oprofilefs_lock, flags);
-        return 0;
+        return count;
 }
 
 
@@ -99,7 +106,7 @@ static ssize_t ulong_write_file(struct file *file, char const __user *buf, size_
                 return -EINVAL;
 
         retval = oprofilefs_ulong_from_user(&value, buf, count);
-        if (retval)
+        if (retval <= 0)
                 return retval;
 
         retval = oprofile_set_ulong(file->private_data, value);