bpf: Do not WARN in bpf_warn_invalid_xdp_action()

The WARN_ONCE() in bpf_warn_invalid_xdp_action() can be triggered by
any bugged program, and even attaching a correct program to a NIC
not supporting the given action.

The resulting splat, beyond polluting the logs, fouls automated tools:
e.g. a syzkaller reproducers using an XDP program returning an
unsupported action will never pass validation.

Replace the WARN_ONCE with a less intrusive pr_warn_once().

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/016ceec56e4817ebb2a9e35ce794d5c917df572c.1638189075.git.pabeni@redhat.com

diff --git a/net/core/filter.c b/net/core/filter.c
index e4cc3aff5bf7054d887a4dd32fb77a94bf3a5a2a..ad8619aa77b7d6ef0ebdb8438379188ec9981b3d 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -8184,9 +8184,9 @@ void bpf_warn_invalid_xdp_action(u32 act)
 {
        const u32 act_max = XDP_REDIRECT;
 
-       WARN_ONCE(1, "%s XDP return value %u, expect packet loss!\n",
-                 act > act_max ? "Illegal" : "Driver unsupported",
-                 act);
+       pr_warn_once("%s XDP return value %u, expect packet loss!\n",
+                    act > act_max ? "Illegal" : "Driver unsupported",
+                    act);
 }
 EXPORT_SYMBOL_GPL(bpf_warn_invalid_xdp_action);