[PATCH AUTOSEL 4.19 29/52] r8152: Set memory to all 0xFFs on failed reg reads

From: Sasha Levin
Date: Wed Sep 04 2019 - 12:01:02 EST

From: Prashant Malani <pmalani@xxxxxxxxxxxx>

[ 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@xxxxxxxxxxxx>
Acked-by: Hayes Wang <hayeswang@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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 f1b5201cc3207..a065a6184f7e4 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -788,8 +788,11 @@ 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),
value, index, tmp, size, 500);
+ if (ret < 0)
+ memset(data, 0xff, size);
+ else
+ memcpy(data, tmp, size);

- memcpy(data, tmp, size);

return ret;