[4.2.y-ckt stable] Patch "remoteproc: avoid stack overflow in debugfs file" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    remoteproc: avoid stack overflow in debugfs file

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 1578d783e365b944ecf2fe577aaca704e4804133 Mon Sep 17 00:00:00 2001
From: Arnd Bergmann <arnd at arndb.de>
Date: Fri, 20 Nov 2015 18:26:07 +0100
Subject: remoteproc: avoid stack overflow in debugfs file

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 at arndb.de>
Fixes: 2e37abb89a2e ("remoteproc: create a 'recovery' debugfs entry")
Signed-off-by: Ohad Ben-Cohen <ohad at wizery.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/remoteproc/remoteproc_debugfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/remoteproc/remoteproc_debugfs.c b/drivers/remoteproc/remoteproc_debugfs.c
index 9d30809..916af50 100644
--- a/drivers/remoteproc/remoteproc_debugfs.c
+++ b/drivers/remoteproc/remoteproc_debugfs.c
@@ -156,7 +156,7 @@ rproc_recovery_write(struct file *filp, const char __user *user_buf,
 	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);
--
1.9.1