linux-kernel - [PATCH 4.2.y-ckt 110/305] remoteproc: avoid stack overflow in debugfs file

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Message-Id: <1452902519-2754-111-git-send-email-kamal@canonical.com>
Date:	Fri, 15 Jan 2016 15:58:44 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Arnd Bergmann <arnd@...db.de>, Ohad Ben-Cohen <ohad@...ery.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 110/305] remoteproc: avoid stack overflow in debugfs file

4.2.8-ckt2 -stable review patch.  If anyone has any objections, please let me know.

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

From: Arnd Bergmann <arnd@...db.de>

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@...db.de>
Fixes: 2e37abb89a2e ("remoteproc: create a 'recovery' debugfs entry")
Signed-off-by: Ohad Ben-Cohen <ohad@...ery.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.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