[PATCH 4.3 020/200] remoteproc: avoid stack overflow in debugfs file

[Greg Kroah-Hartman]

4.3-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@xxxxxxxx>

commit 92792e48e2ae6051af30468a87994b5432da2f06 upstream.

Recent gcc versions warn about reading from a negative offset of
an on-stack array:

drivers/remoteproc/remoteproc_debugfs.c: In function 'rproc_recovery_write':
drivers/remoteproc/remoteproc_debugfs.c:167:9: warning: 'buf[4294967295u]' may be used uninitialized in this function [-Wmaybe-uninitialized]

I don't see anything in sys_write() that prevents us from
being called with a zero 'count' argument, so we should
add an extra check in rproc_recovery_write() to prevent the
access and avoid the warning.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Fixes: 2e37abb89a2e ("remoteproc: create a 'recovery' debugfs entry")
Signed-off-by: Ohad Ben-Cohen <ohad@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/remoteproc/remoteproc_debugfs.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/remoteproc/remoteproc_debugfs.c
+++ b/drivers/remoteproc/remoteproc_debugfs.c
@@ -156,7 +156,7 @@ rproc_recovery_write(struct file *filp,
 	char buf[10];
 	int ret;
 
-	if (count > sizeof(buf))
+	if (count < 1 || count > sizeof(buf))
 		return count;
 
 	ret = copy_from_user(buf, user_buf, count);