bpf: Do not WARN in bpf_warn_invalid_xdp_action()

BugLink: https://bugs.launchpad.net/bugs/1959376
[ Upstream commit 2cbad989033bff0256675c38f96f5faab852af4b ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/net/core/filter.c b/net/core/filter.c
index 1e43ab413b62ec2ab6314b7b24f2fa1a04afd2fb..f207e4782bd0ef581af12fe4a185f25b398a1f20 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -8178,9 +8178,9 @@ 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);