From nobody Sun Oct 5 01:52:27 2025 Received: from mail.cyberchaos.dev (mail.cyberchaos.dev [195.39.247.168]) (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 068DB374EA; Mon, 11 Aug 2025 09:40:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.39.247.168 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754905211; cv=none; b=u4/3w+bgpWfToCS0e0KrRbwFUQT2dSqQaa07QqitkrnRLKAG2XtcZm6eg0qfT5xsxwtxzx05CE5LNlQ8GGbHCtp/UZWOaoCPeJKGV3SuGsPzt1N6+J6MkuZvGN7foxwMRNCcolXu1QqYqIfZPdOUjwwYkcgJlu6FVYTEVcRKy8k= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754905211; c=relaxed/simple; bh=uCJtmPEFzY+QWjgExO8MW8+SvPrYxIduutknzX5sQKg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Fqvl0wmY6OOLWZQZnrKfz0if3QUKhVQ3uO5xXBQhyWFD7PYYMPQGvQD5g7YOeWDM6dEBc7xuqYFPfIeJMpVtFBY4nPOlWLJ2Y7ifzDa7ehDTeDAmRMV0WS4JHdohCCmkbPIEO9vxRsHuA9b6kSQw0Fo5PUrstqgeQ6iFIzNtY/k= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=yuka.dev; spf=pass smtp.mailfrom=yuka.dev; dkim=pass (1024-bit key) header.d=yuka.dev header.i=@yuka.dev header.b=jxyTIrUs; arc=none smtp.client-ip=195.39.247.168 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=yuka.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=yuka.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=yuka.dev header.i=@yuka.dev header.b="jxyTIrUs" From: Yureka Lilian DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yuka.dev; s=mail; t=1754905206; 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=FU6aEs8zwpQqV/O36lHWhC0ilYDhDHPiAL8/2sMKVS8=; b=jxyTIrUs7YwDk7yYAQJJiJxjWCtET/D66F5zYINIm0pbLPLyNOyrD7dAKtP7AxQ47czp8y /21Ng0L0GMp38sPHbFyDMVve4G6HEr7jB6uRPNHA5IfAqfNsQanuvGM4RcAfEsY6mleLND lGIUEoV603BcUrsWZlh3O60mR28Wlpc= To: Andrii Nakryiko , Eduard Zingerman , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa Cc: Yureka Lilian , bpf@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] bpf: fix reuse of DEVMAP Date: Mon, 11 Aug 2025 11:39:44 +0200 Message-ID: <20250811093945.41028-1-yuka@yuka.dev> In-Reply-To: <20250811091046.35696-1-yuka@yuka.dev> References: <20250811091046.35696-1-yuka@yuka.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Previously, re-using pinned DEVMAP maps would always fail, because get_map_info on a DEVMAP always returns flags with BPF_F_RDONLY_PROG set, it BPF_F_RDONLY_PROG being set on a map being created is invalid. Thus, match the BPF_F_RDONLY_PROG flag being set on the new map when checking for compatibility with an existing DEVMAP The same problem is handled in third-party ebpf library: - https://github.com/cilium/ebpf/issues/925 - https://github.com/cilium/ebpf/pull/930 Signed-off-by: Yureka Lilian --- tools/lib/bpf/libbpf.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index fb4d92c5c..a554d7fff 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -5081,6 +5081,7 @@ static bool map_is_reuse_compat(const struct bpf_map = *map, int map_fd) { struct bpf_map_info map_info; __u32 map_info_len =3D sizeof(map_info); + __u32 map_flags_for_check =3D map->def.map_flags; int err; =20 memset(&map_info, 0, map_info_len); @@ -5093,11 +5094,20 @@ static bool map_is_reuse_compat(const struct bpf_ma= p *map, int map_fd) return false; } =20 + /* get_map_info on a DEVMAP will always return flags with + * BPF_F_RDONLY_PROG set, but it will never be set on a map + * being created. + * Thus, match the BPF_F_RDONLY_PROG flag being set on the new + * map when checking for compatibility with an existing DEVMAP + */ + if (map->def.type =3D=3D BPF_MAP_TYPE_DEVMAP || map->def.type =3D=3D BPF_= MAP_TYPE_DEVMAP_HASH) + map_flags_for_check |=3D BPF_F_RDONLY_PROG; + return (map_info.type =3D=3D map->def.type && map_info.key_size =3D=3D map->def.key_size && map_info.value_size =3D=3D map->def.value_size && map_info.max_entries =3D=3D map->def.max_entries && - map_info.map_flags =3D=3D map->def.map_flags && + map_info.map_flags =3D=3D map_flags_for_check && map_info.map_extra =3D=3D map->map_extra); } =20 --=20 2.50.1