[PATCH 4.19 20/51] xfrm: enforce validity of offload input flags

[Greg Kroah-Hartman]

From: Leon Romanovsky <leonro@xxxxxxxxxx>

commit 7c76ecd9c99b6e9a771d813ab1aa7fa428b3ade1 upstream.

struct xfrm_user_offload has flags variable that received user input,
but kernel didn't check if valid bits were provided. It caused a situation
where not sanitized input was forwarded directly to the drivers.

For example, XFRM_OFFLOAD_IPV6 define that was exposed, was used by
strongswan, but not implemented in the kernel at all.

As a solution, check and sanitize input flags to forward
XFRM_OFFLOAD_INBOUND to the drivers.

Fixes: d77e38e612a0 ("xfrm: Add an IPsec hardware offloading API")
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
Signed-off-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 include/uapi/linux/xfrm.h |    6 ++++++
 net/xfrm/xfrm_device.c    |    6 +++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

--- a/include/uapi/linux/xfrm.h
+++ b/include/uapi/linux/xfrm.h
@@ -504,6 +504,12 @@ struct xfrm_user_offload {
 	int				ifindex;
 	__u8				flags;
 };
+/* This flag was exposed without any kernel code that supporting it.
+ * Unfortunately, strongswan has the code that uses sets this flag,
+ * which makes impossible to reuse this bit.
+ *
+ * So leave it here to make sure that it won't be reused by mistake.
+ */
 #define XFRM_OFFLOAD_IPV6	1
 #define XFRM_OFFLOAD_INBOUND	2
 
--- a/net/xfrm/xfrm_device.c
+++ b/net/xfrm/xfrm_device.c
@@ -153,6 +153,9 @@ int xfrm_dev_state_add(struct net *net,
 	if (x->encap || x->tfcpad)
 		return -EINVAL;
 
+	if (xuo->flags & ~(XFRM_OFFLOAD_IPV6 | XFRM_OFFLOAD_INBOUND))
+		return -EINVAL;
+
 	dev = dev_get_by_index(net, xuo->ifindex);
 	if (!dev) {
 		if (!(xuo->flags & XFRM_OFFLOAD_INBOUND)) {
@@ -190,7 +193,8 @@ int xfrm_dev_state_add(struct net *net,
 
 	xso->dev = dev;
 	xso->num_exthdrs = 1;
-	xso->flags = xuo->flags;
+	/* Don't forward bit that is not implemented */
+	xso->flags = xuo->flags & ~XFRM_OFFLOAD_IPV6;
 
 	err = dev->xfrmdev_ops->xdo_dev_state_add(x);
 	if (err) {