netdev - [PATCH net-next v2 1/2] bpf: do not WARN in bpf_warn_invalid_xdp

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Message-Id: <1817b31eac5f1b10abb2870ff09ed6af4814ef01.1637924200.git.pabeni@redhat.com>
Date:   Fri, 26 Nov 2021 12:19:10 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, bpf@...r.kernel.org,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: [PATCH net-next v2 1/2] 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().

Acked-by: Toke Høiland-Jørgensen <toke@...hat.com>
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 net/core/filter.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 8271624a19aa..5631acf3f10c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -8185,9 +8185,9 @@ 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);
 
-- 
2.33.1