netdev - [PATCH AUTOSEL 4.9 13/27] r8152: Set memory to all 0xFFs on failed reg reads

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Date:   Wed,  4 Sep 2019 12:02:06 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Prashant Malani <pmalani@...omium.org>,
        Hayes Wang <hayeswang@...ltek.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, linux-usb@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.9 13/27] r8152: Set memory to all 0xFFs on failed reg reads

From: Prashant Malani <pmalani@...omium.org>

[ Upstream commit f53a7ad189594a112167efaf17ea8d0242b5ac00 ]

get_registers() blindly copies the memory written to by the
usb_control_msg() call even if the underlying urb failed.

This could lead to junk register values being read by the driver, since
some indirect callers of get_registers() ignore the return values. One
example is:
  ocp_read_dword() ignores the return value of generic_ocp_read(), which
  calls get_registers().

So, emulate PCI "Master Abort" behavior by setting the buffer to all
0xFFs when usb_control_msg() fails.

This patch is copied from the r8152 driver (v2.12.0) published by
Realtek (www.realtek.com).

Signed-off-by: Prashant Malani <pmalani@...omium.org>
Acked-by: Hayes Wang <hayeswang@...ltek.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/usb/r8152.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 02e29562d254e..15dc70c118579 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -689,8 +689,11 @@ int get_registers(struct r8152 *tp, u16 value, u16 index, u16 size, void *data)
 	ret = usb_control_msg(tp->udev, usb_rcvctrlpipe(tp->udev, 0),
 			      RTL8152_REQ_GET_REGS, RTL8152_REQT_READ,
 			      value, index, tmp, size, 500);
+	if (ret < 0)
+		memset(data, 0xff, size);
+	else
+		memcpy(data, tmp, size);
 
-	memcpy(data, tmp, size);
 	kfree(tmp);
 
 	return ret;
-- 
2.20.1