net: xdp: Disallow attaching device-bound programs in generic mode

Device-bound programs are used to support RX metadata kfuncs. These
kfuncs are driver-specific and rely on the driver context to read the
metadata. This means they can't work in generic XDP mode. However, there
is no check to disallow such programs from being attached in generic
mode, in which case the metadata kfuncs will be called in an invalid
context, leading to crashes.

Fix this by adding a check to disallow attaching device-bound programs
in generic mode.

Fixes: 2b3486bc2d23 ("bpf: Introduce device-bound XDP programs")
Reported-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
Closes: https://lore.kernel.org/r/dae862ec-43b5-41a0-8edf-46c59071cdda@hetzner-cloud.de
Tested-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20250127131344.238147-1-toke@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/dev.c b/net/core/dev.c
index 07b2bb1ce64ff79894fae8cca044ff9ed0cc3786..02cd75b512f9277b2cdfabd51bca056b2ee69639 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -9924,6 +9924,10 @@ static int dev_xdp_attach(struct net_device *dev, struct netlink_ext_ack *extack
                        NL_SET_ERR_MSG(extack, "Program bound to different device");
                        return -EINVAL;
                }
+               if (bpf_prog_is_dev_bound(new_prog->aux) && mode == XDP_MODE_SKB) {
+                       NL_SET_ERR_MSG(extack, "Can't attach device-bound programs in generic mode");
+                       return -EINVAL;
+               }
                if (new_prog->expected_attach_type == BPF_XDP_DEVMAP) {
                        NL_SET_ERR_MSG(extack, "BPF_XDP_DEVMAP programs can not be attached to a device");
                        return -EINVAL;