[PATCH net-next 10/13] nfp: validate rx offset from the BAR and size down it's field

[Jakub Kicinski]

NFP_NET_CFG_RX_OFFSET is 32bit wide, make sure what we read from
there is reasonable for packet headroom.  This allows us to store
the rx_offset in a 8bit variable.

Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.com>
---
 drivers/net/ethernet/netronome/nfp/nfp_net.h        |  6 +++---
 drivers/net/ethernet/netronome/nfp/nfp_net_common.c | 14 +++++++++++---
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net.h 
b/drivers/net/ethernet/netronome/nfp/nfp_net.h
index db92463da440..5f0547c6efb8 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net.h
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net.h
@@ -439,9 +439,9 @@ struct nfp_stat_pair {
  * @bpf_offload_xdp:   Offloaded BPF program is XDP
  * @chained_metadata_format:  Firemware will use new metadata format
  * @rx_dma_dir:                Mapping direction for RX buffers
+ * @rx_offset:         Offset in the RX buffers where packet data starts
  * @ctrl:              Local copy of the control register/word.
  * @fl_bufsz:          Currently configured size of the freelist buffers
- * @rx_offset:         Offset in the RX buffers where packet data starts
  * @xdp_prog:          Installed XDP program
  * @tx_rings:          Array of pre-allocated TX ring structures
  * @rx_rings:          Array of pre-allocated RX ring structures
@@ -466,11 +466,11 @@ struct nfp_net_dp {
 
        u8 rx_dma_dir;
 
+       u8 rx_offset;
+
        u32 ctrl;
        u32 fl_bufsz;
 
-       u32 rx_offset;
-
        struct bpf_prog *xdp_prog;
 
        struct nfp_net_tx_ring *tx_rings;
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c 
b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
index ab03f2f301cd..513f55dd746b 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_common.c
@@ -3124,10 +3124,18 @@ int nfp_net_netdev_init(struct net_device *netdev)
        nfp_net_write_mac_addr(nn);
 
        /* Determine RX packet/metadata boundary offset */
-       if (nn->fw_ver.major >= 2)
-               nn->dp.rx_offset = nn_readl(nn, NFP_NET_CFG_RX_OFFSET);
-       else
+       if (nn->fw_ver.major >= 2) {
+               u32 reg;
+
+               reg = nn_readl(nn, NFP_NET_CFG_RX_OFFSET);
+               if (reg > NFP_NET_MAX_PREPEND) {
+                       nn_err(nn, "Invalid rx offset: %d\n", reg);
+                       return -EINVAL;
+               }
+               nn->dp.rx_offset = reg;
+       } else {
                nn->dp.rx_offset = NFP_NET_RX_OFFSET;
+       }
 
        /* Set default MTU and Freelist buffer size */
        if (nn->max_mtu < NFP_NET_DEFAULT_MTU)
-- 
2.11.0