linux-kernel - [PATCH] bpf: do not inline bpf_get_smp_processor_id() with CONFIG

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Message-ID: <20241216104615.503706-1-arighi@nvidia.com>
Date: Mon, 16 Dec 2024 11:46:15 +0100
From: Andrea Righi <arighi@...dia.com>
To: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>
Cc: John Fastabend <john.fastabend@...il.com>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] bpf: do not inline bpf_get_smp_processor_id() with CONFIG_SMP disabled

Calling bpf_get_smp_processor_id() in a kernel with CONFIG_SMP disabled
can trigger the following bug, as pcpu_hot is unavailable:

[    8.471774] BUG: unable to handle page fault for address: 00000000936a290c
[    8.471849] #PF: supervisor read access in kernel mode
[    8.471881] #PF: error_code(0x0000) - not-present page

Fix by preventing the inlining of bpf_get_smp_processor_id() when
CONFIG_SMP disabled.

Fixes: 1ae6921009e5 ("bpf: inline bpf_get_smp_processor_id() helper")
Signed-off-by: Andrea Righi <arighi@...dia.com>
---
 kernel/bpf/verifier.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index f7f892a52a37..d85413f1a784 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -21272,7 +21272,7 @@ static int do_misc_fixups(struct bpf_verifier_env *env)
 			goto next_insn;
 		}
 
-#if defined(CONFIG_X86_64) && !defined(CONFIG_UML)
+#if defined(CONFIG_SMP) && defined(CONFIG_X86_64) && !defined(CONFIG_UML)
 		/* Implement bpf_get_smp_processor_id() inline. */
 		if (insn->imm == BPF_FUNC_get_smp_processor_id &&
 		    verifier_inlines_helper_call(env, insn->imm)) {
-- 
2.47.1