linux-kernel - [PATCH 5.15 548/846] bpf: Do not WARN in bpf_warn_invalid_xdp

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Date:   Mon, 24 Jan 2022 19:41:05 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Paolo Abeni <pabeni@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 548/846] bpf: Do not WARN in bpf_warn_invalid_xdp_action()

From: Paolo Abeni <pabeni@...hat.com>

[ 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@...hat.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: Toke Høiland-Jørgensen <toke@...hat.com>
Link: https://lore.kernel.org/bpf/016ceec56e4817ebb2a9e35ce794d5c917df572c.1638189075.git.pabeni@redhat.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 1e43ab413b62e..f207e4782bd0e 100644
--- 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);
 
-- 
2.34.1