From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta0.migadu.com (out-182.mta0.migadu.com [91.218.175.182]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7D6FB37883D for ; Wed, 22 Jul 2026 15:19:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784733598; cv=none; b=TAsJhtvAAOT1S/lUg0hwk+Sx9p8C7QmPy2jDe8xYQTsMQaL0NyDQhqdC9ncxGRUuWIaBxwcQD4+aPeFVYAeSiAlVD6kHrPsD3FOSCG+BJewK6v4qTUWMuBVskG564Y12dawbxsaUO3pCY6oz/xoEjwZ/S47DCavZ5N7kAs+W+ms= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784733598; c=relaxed/simple; bh=i5Y8LBLIVi9NZXbiFyUAigdwHHkCtn2fo3m5k7f1Kac=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=sNg5hdPj5De8loM4WG4nLeL+uJ5L85yfL44hnGIAIFQ1eP/aoI3lhBMBjvPkrT9lwaRsZHjRf6U0oKlpXvqN/jbOVGxEF5Aq+N6RE/yDVeR60XpRxRi88ib1yU8xVGz3MDN0equ8SUom7l97yGGwOfFf6Kvx+g/dMZY8KzYa6dM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=rP6SWJRw; arc=none smtp.client-ip=91.218.175.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="rP6SWJRw" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1784733591; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hYTgWVcRbrysugLURttWCpGcYz3LG4GprKcAXdzH1sw=; b=rP6SWJRw4mfP9qp8M+vv00V5zK6gxv7Bl7QQOcJBP0RTHEqhD6DOiubdBnUG5+mqWjxNHT lXm34jmVUjHJMDbBLYmpcT8HbIYW5faznwfTv6eDvShX9RSJ5I4EIPuqJvniBaCI77vXQO aGuxT/AYa1cLQcYU5qvKMH2e44UHWos= From: Leon Hwang To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Martin KaFai Lau , Song Liu , Yonghong Song , Jiri Olsa , Emil Tsalapatis , Shuah Khan , Jingguo Tan , Pu Lehui , Leon Hwang , Lin Ma , Maciej Fijalkowski , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, kernel-patches-bot@fb.com Subject: [PATCH bpf-next v2 1/2] bpf: Fix WARNING in bpf_tracing_link_release Date: Wed, 22 Jul 2026 23:19:08 +0800 Message-ID: <20260722151909.69142-2-leon.hwang@linux.dev> In-Reply-To: <20260722151909.69142-1-leon.hwang@linux.dev> References: <20260722151909.69142-1-leon.hwang@linux.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT The trampoline could be corrupted by the blindly 'tr->flags = BPF_TRAMP_F_TAIL_CALL_CTX' in verifier. 1. A fexit attached to a tail_call_reachable prog. 'tr->flags' became 'BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_TAIL_CALL_CTX'. And, the trampoline would poke the target prog's nop insn using jmp insn instead of call insn. 2. Another fexit loaded with the same tail_call_reachable prog target. 'tr->flags' became 'BPF_TRAMP_F_TAIL_CALL_CTX'. 3. Close the first fexit link. Due to no BPF_TRAMP_F_CALL_ORIG in 'tr->flags', the trampoline will fail to restore the prog's nop insn using call insn. [ 3.410719] WARNING: kernel/bpf/syscall.c:3551 at bpf_tracing_link_release+0x53/0x60, CPU#1: test_progs/98 ... [ 3.428793] bpf_link_free+0x58/0x130 [ 3.429293] bpf_link_release+0x23/0x30 Fix the warning by updating 'tr->flags' with '|=' and lock. Fixes: 2b5dcb31a19a ("bpf, x64: Fix tailcall infinite loop") Acked-by: Jiri Olsa Signed-off-by: Leon Hwang --- include/linux/bpf.h | 2 ++ kernel/bpf/trampoline.c | 7 +++++++ kernel/bpf/verifier.c | 2 +- 3 files changed, 10 insertions(+), 1 deletion(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index e066f44a9c05..7bfc28673124 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1523,6 +1523,7 @@ int bpf_trampoline_multi_attach(struct bpf_prog *prog, u32 *ids, struct bpf_tracing_multi_link *link); int bpf_trampoline_multi_detach(struct bpf_prog *prog, struct bpf_tracing_multi_link *link); +void bpf_trampoline_set_flags(struct bpf_trampoline *tr, u32 flags); /* * When the architecture supports STATIC_CALL replace the bpf_dispatcher_fn @@ -1646,6 +1647,7 @@ static inline int bpf_trampoline_multi_detach(struct bpf_prog *prog, { return -ENOTSUPP; } +static inline void bpf_trampoline_set_flags(struct bpf_trampoline *tr, u32 flags) {} #endif struct bpf_func_info_aux { diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index 6eadf64f7ec9..129d07db117e 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -670,6 +670,13 @@ static struct bpf_tramp_image *bpf_tramp_image_alloc(u64 key, int size) return ERR_PTR(err); } +void bpf_trampoline_set_flags(struct bpf_trampoline *tr, u32 flags) +{ + trampoline_lock(tr); + tr->flags |= flags; + trampoline_unlock(tr); +} + static int bpf_trampoline_update(struct bpf_trampoline *tr, bool lock_direct_mutex, const struct bpf_trampoline_ops *ops, void *data) { diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 52be0a118cce..66d8d9eaec05 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -19523,7 +19523,7 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) return -ENOMEM; if (tgt_prog && tgt_prog->aux->tail_call_reachable) - tr->flags = BPF_TRAMP_F_TAIL_CALL_CTX; + bpf_trampoline_set_flags(tr, BPF_TRAMP_F_TAIL_CALL_CTX); prog->aux->dst_trampoline = tr; return 0; -- 2.55.0