From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 E12D9343893; Sat, 12 Sep 2026 09:53:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789206804; cv=none; b=S6IfW5vW6iCPB0G7w++eyE74CghXZCCGIPY/qW51KuNphyIOwANxb1Jn6X9zAMutrZxSHz086gN+C6OEqxmqvpyQ0Md8uybsmSVLEuim/NrRDFcMJVGQo9912iXOongfw1vr7XYG9htCA0u5x1WH4OLR0tgk5r1NaXzKwnTAQ20= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789206804; c=relaxed/simple; bh=dEw1j8VgYq2javOSU24RLiorU720PNh58PGY7MFXwgA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kFTzi8Wf2bnQPNwGIDvIVUUcuHgtuRbMZBCgvegiifHBRYs+Uj4SrtNapHR530NLjT2VsXZyDlFjm1TCEDx9QOhkUGMGigVy0CKOy6gFMG049Z1zj/4GlDXkQL/h9NpEDoKkIGO4yPuiads9HXeid3ez2b7iGH8v0WNfQ0PJrac= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=uElyvYwy; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="uElyvYwy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E31B01F000FF; Sat, 12 Sep 2026 09:53:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789206802; bh=Ns6g5mT1HQFc57qyJMFD94EH0z7MH0dVo4SKeBV32KE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=uElyvYwy7cQPQL1pkHWqgVsp5ksX4cM3zCfXw0y9SzUhN8DNFFvyybkLTp1O2Rx8A ZmucPPtljCkKpwL0B/Pi/0RoIYhoXPjKPqyi18Nnj4StXtvKnh8KvyLgNfXFIfseNo o3OyizM1EGFk+xj4ORAVETcyHd1SSgHzpXhtMP8E= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Daniel Borkmann , Kumar Kartikeya Dwivedi , Sasha Levin Subject: [PATCH 6.18 0275/1518] bpf: Fix vmlinux BTF prep race in bpf_get_btf_vmlinux Date: Sat, 12 Sep 2026 08:40:44 +0200 Message-ID: <20260912065629.704360727@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065623.398859879@linuxfoundation.org> References: <20260912065623.398859879@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Borkmann [ Upstream commit 92863e678070f57c17c868e4bfa2441a5c61ad2b ] bpf_get_btf_vmlinux() lazily parses the vmlinux BTF under the bpf_verifier_lock, but publishes the result through a plain store and re-checks it through a plain lockless load. Nothing orders the stores initializing the struct btf inside btf_parse_vmlinux() against the store publishing the pointer: On a weakly ordered arch, a concurrent first-time caller taking the lockless fast path could in principle observe the pointer before the parsed contents are visible. The mutex_unlock() does not help such a reader given it only synchronizes with a later acquisition of the same lock. Thus, publish the pointer with smp_store_release() and read it on the fast path with smp_load_acquire(). Acquire semantics are needed rather than a dependency-ordered READ_ONCE(): btf_parse_vmlinux() also populates globals outside the returned object (e.g. bpf_ctx_convert.t). An address dependency would only order accesses performed through the pointer and not cover other globals. Fixes: 8580ac9404f6 ("bpf: Process in-kernel BTF") Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20260708211537.371874-2-daniel@iogearbox.net Signed-off-by: Kumar Kartikeya Dwivedi Signed-off-by: Sasha Levin --- kernel/bpf/verifier.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 140be10eeb7bf..3be56a023a1bc 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -24406,13 +24406,25 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) struct btf *bpf_get_btf_vmlinux(void) { - if (!btf_vmlinux && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) { + /* Pairs with the smp_store_release() on the parse path below. */ + struct btf *btf = smp_load_acquire(&btf_vmlinux); + + if (!btf && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) { mutex_lock(&bpf_verifier_lock); - if (!btf_vmlinux) - btf_vmlinux = btf_parse_vmlinux(); + btf = btf_vmlinux; + if (!btf) { + btf = btf_parse_vmlinux(); + /* + * Order the parsed BTF contents and the globals the + * parse populated (e.g. bpf_ctx_convert.t) before + * the pointer publication. Pairs with the acquire + * on the lockless fast path above. + */ + smp_store_release(&btf_vmlinux, btf); + } mutex_unlock(&bpf_verifier_lock); } - return btf_vmlinux; + return btf; } /* -- 2.53.0