[PATCH] oprofilefs: Handle zero-length writes.

[Mike Waychison <mikew@google.com>]

Currently in oprofilefs, files that use ulong_fops mis-handle writes of
zero length.  A count of 0 causes oprofilefs_ulong_from_user to return
0 (success), which then leads to oprofile_set_ulong being called to
stuff "value" into file->private_data without it being initialized.

Fix this by moving the check for a zero-length write up into
ulong_write_file.

Signed-off-by: Mike Waychison <mikew@google.com>
---
 drivers/oprofile/oprofilefs.c |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/oprofile/oprofilefs.c b/drivers/oprofile/oprofilefs.c
index e9ff6f7..ee14e6e 100644
--- a/drivers/oprofile/oprofilefs.c
+++ b/drivers/oprofile/oprofilefs.c
@@ -65,9 +65,6 @@ int oprofilefs_ulong_from_user(unsigned long *val, char const __user *buf, size_
 	char tmpbuf[TMPBUFSIZE];
 	unsigned long flags;
 
-	if (!count)
-		return 0;
-
 	if (count > TMPBUFSIZE - 1)
 		return -EINVAL;
 
@@ -97,6 +94,8 @@ static ssize_t ulong_write_file(struct file *file, char const __user *buf, size_
 
 	if (*offset)
 		return -EINVAL;
+	if (count == 0)
+		return 0;
 
 	retval = oprofilefs_ulong_from_user(&value, buf, count);
 	if (retval)
-- 
1.7.3.1