Add a couple of things:
1. Remove xdp_umem_reg_v2 since its sizeof is the same as xdp_umem_reg
2. Add BUILD_BUG_ON that checks that the size of xdp_umem_reg_v1 is less
than xdp_umem_reg; presumably, when we get to v2, there is gonna
be a similar line to enforce that sizeof(v2) > sizeof(v1)
3. Add BUILD_BUG_ON to make sure the last field plus its size matches
the overall struct size. The intent is to demonstrate that we don't
have any lingering padding.
Reported-by: Julian Schindel <mail@xxxxxxxxxxxxxxxx>
Cc: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxxx>
---
net/xdp/xsk.c | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 7d1c0986f9bb..1d951d7e3797 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -1331,14 +1331,6 @@ struct xdp_umem_reg_v1 {
__u32 headroom;
};
-struct xdp_umem_reg_v2 {
- __u64 addr; /* Start of packet data area */
- __u64 len; /* Length of packet data area */
- __u32 chunk_size;
- __u32 headroom;
- __u32 flags;
-};
-
static int xsk_setsockopt(struct socket *sock, int level, int optname,
sockptr_t optval, unsigned int optlen)
{
@@ -1382,10 +1374,19 @@ static int xsk_setsockopt(struct socket *sock, int level, int optname,
if (optlen < sizeof(struct xdp_umem_reg_v1))
return -EINVAL;
- else if (optlen < sizeof(struct xdp_umem_reg_v2))
- mr_size = sizeof(struct xdp_umem_reg_v1);
else if (optlen < sizeof(mr))
- mr_size = sizeof(struct xdp_umem_reg_v2);
+ mr_size = sizeof(struct xdp_umem_reg_v1);
+
+ BUILD_BUG_ON(sizeof(struct xdp_umem_reg_v1) >= sizeof(struct xdp_umem_reg));
+
+ /* Make sure the last field of the struct doesn't have
+ * uninitialized padding. All padding has to be explicit
+ * and has to be set to zero by the userspace to make
+ * struct xdp_umem_reg extensible in the future.
+ */
+ BUILD_BUG_ON(offsetof(struct xdp_umem_reg, tx_metadata_len) +
+ sizeof_field(struct xdp_umem_reg, tx_metadata_len) !=
+ sizeof(struct xdp_umem_reg));
if (copy_from_sockptr(&mr, optval, mr_size))
return -EFAULT;
--
2.45.2
