[PATCH 5.4 20/64] xfrm: enforce validity of offload input flags

Greg Kroah-Hartman
2022-03-07T09:36:00Z

From: Leon Romanovsky <leonro@nvidia.com>

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@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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
@@ -206,6 +206,9 @@ 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)) {
@@ -243,7 +246,8 @@ 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) {