From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 DD21BBA49 for ; Tue, 7 Mar 2023 18:47:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 42A87C433EF; Tue, 7 Mar 2023 18:47:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1678214864; bh=SO4TmPjTGtVmyOChUjSxE5JOC3EGu+TuYBlqo+fZzUE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=L5cfN/iB+MyS5IQ4DZzRKL0S+D8mGuA7IVhXROfldyOcZJ4OUm54I1JELhDXEjgfo /20I6CQ8Wsg+Zy+Le8hpOy5BP0nH3T+Qv9NBu+07GRdWQUg7XxlBPAPGnxn96cB16a jP75Hml6YOPB6zyax267t949Vx+QFsbHzgpqNTR8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Andrii Nakryiko , Daniel Borkmann , Sasha Levin Subject: [PATCH 5.15 074/567] libbpf: Fix btf__align_of() by taking into account field offsets Date: Tue, 7 Mar 2023 17:56:50 +0100 Message-Id: <20230307165909.108375933@linuxfoundation.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230307165905.838066027@linuxfoundation.org> References: <20230307165905.838066027@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Andrii Nakryiko [ Upstream commit 25a4481b4136af7794e1df2d6c90ed2f354d60ce ] btf__align_of() is supposed to be return alignment requirement of a requested BTF type. For STRUCT/UNION it doesn't always return correct value, because it calculates alignment only based on field types. But for packed structs this is not enough, we need to also check field offsets and struct size. If field offset isn't aligned according to field type's natural alignment, then struct must be packed. Similarly, if struct size is not a multiple of struct's natural alignment, then struct must be packed as well. This patch fixes this issue precisely by additionally checking these conditions. Fixes: 3d208f4ca111 ("libbpf: Expose btf__align_of() API") Signed-off-by: Andrii Nakryiko Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20221212211505.558851-5-andrii@kernel.org Signed-off-by: Sasha Levin --- tools/lib/bpf/btf.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 3ed759f53e7c2..fd23095129782 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -647,8 +647,21 @@ int btf__align_of(const struct btf *btf, __u32 id) if (align <= 0) return libbpf_err(align); max_align = max(max_align, align); + + /* if field offset isn't aligned according to field + * type's alignment, then struct must be packed + */ + if (btf_member_bitfield_size(t, i) == 0 && + (m->offset % (8 * align)) != 0) + return 1; } + /* if struct/union size isn't a multiple of its alignment, + * then struct must be packed + */ + if ((t->size % max_align) != 0) + return 1; + return max_align; } default: -- 2.39.2