xsk: Validate xsk_tx_metadata flags

Accept only the flags that the kernel knows about to make
sure we can extend this field in the future. Note that only
in XDP_COPY mode we propagate the error signal back to the user
(via sendmsg). For zerocopy mode we silently skip the metadata
for the descriptors that have wrong flags (since we process
the descriptors deep in the driver).

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20231127190319.1190813-8-sdf@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
index e2558ac3e195a982744eeb227024014ac01b3d85..81e02de3f45377946dd80c2335666128af7f9bbb 100644 (file)
--- a/include/net/xdp_sock_drv.h
+++ b/include/net/xdp_sock_drv.h
@@ -165,12 +165,28 @@ static inline void *xsk_buff_raw_get_data(struct xsk_buff_pool *pool, u64 addr)
        return xp_raw_get_data(pool, addr);
 }
 
+#define XDP_TXMD_FLAGS_VALID ( \
+               XDP_TXMD_FLAGS_TIMESTAMP | \
+               XDP_TXMD_FLAGS_CHECKSUM | \
+       0)
+
+static inline bool xsk_buff_valid_tx_metadata(struct xsk_tx_metadata *meta)
+{
+       return !(meta->flags & ~XDP_TXMD_FLAGS_VALID);
+}
+
 static inline struct xsk_tx_metadata *xsk_buff_get_metadata(struct xsk_buff_pool *pool, u64 addr)
 {
+       struct xsk_tx_metadata *meta;
+
        if (!pool->tx_metadata_len)
                return NULL;
 
-       return xp_raw_get_data(pool, addr) - pool->tx_metadata_len;
+       meta = xp_raw_get_data(pool, addr) - pool->tx_metadata_len;
+       if (unlikely(!xsk_buff_valid_tx_metadata(meta)))
+               return NULL; /* no way to signal the error to the user */
+
+       return meta;
 }
 
 static inline void xsk_buff_dma_sync_for_cpu(struct xdp_buff *xdp, struct xsk_buff_pool *pool)
@@ -332,6 +348,11 @@ static inline void *xsk_buff_raw_get_data(struct xsk_buff_pool *pool, u64 addr)
        return NULL;
 }
 
+static inline bool xsk_buff_valid_tx_metadata(struct xsk_tx_metadata *meta)
+{
+       return false;
+}
+
 static inline struct xsk_tx_metadata *xsk_buff_get_metadata(struct xsk_buff_pool *pool, u64 addr)
 {
        return NULL;

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index e83ade32f1fda44bfaa0f4dc2485329a27d6ed43..d66ba9d6154f9e346b020b141940d7c4f7d210bb 100644 (file)
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -728,6 +728,10 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
                        }
 
                        meta = buffer - xs->pool->tx_metadata_len;
+                       if (unlikely(!xsk_buff_valid_tx_metadata(meta))) {
+                               err = -EINVAL;
+                               goto free_err;
+                       }
 
                        if (meta->flags & XDP_TXMD_FLAGS_CHECKSUM) {
                                if (unlikely(meta->request.csum_start +