From mboxrd@z Thu Jan 1 00:00:00 1970 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 695422DCF76 for ; Mon, 11 Aug 2025 09:11:27 +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=1754903490; cv=none; b=HUr2pRIM6CP3o49MqYhe6l6PgWsbb52BbQpZ4bYqTZVlG7j/R3LMMReu5Fud17nP/O3qPXvumNMPmGI0k6SKSWhYuLVkJ2G8dkIHE9dIpk4PFMIdX5+qCVQut0NqS6zXNKHKRyuCF72OgtuV91gASOZBMptDX4JopDWywc63S78= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1754903490; c=relaxed/simple; bh=uCJtmPEFzY+QWjgExO8MW8+SvPrYxIduutknzX5sQKg=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=aBhGfIQy4wy8QkL33l+jEWkGkhIj38g0ukga8LsDYi/FQIwlHSpDFtiLF8SGDBT7+VgX5N1BRU+r4wRb683GEN1vWzJekiYr9wT7Wz33GGffxMOMBFUAA3lL6DycAFBcCu6pV7HdbDVZVpFnWU+KbKG1L/DB8CPdkGVEsqCaMP0= 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=md1645lh; 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="md1645lh" From: Yureka Lilian DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yuka.dev; s=mail; t=1754903484; 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; bh=FU6aEs8zwpQqV/O36lHWhC0ilYDhDHPiAL8/2sMKVS8=; b=md1645lh50Rqn9fltNKbli+Iltmz4zOhqPdqfox170IYLZgP8mK/pq5sHZg4cnRzj5kgWS qdW+/jlxpK22+DQ+vn8WYDaK8OKPe+XUQ//ZOTJQdjSuEQI3fKTJO0i7bzbBm9z0TICMIF NYtsW1iCRimsblQ16KJDjt3+u2e21Ro= To: bpf@vger.kernel.org Cc: Yureka Lilian Subject: [PATCH] bpf: fix reuse of DEVMAP Date: Mon, 11 Aug 2025 11:10:18 +0200 Message-ID: <20250811091046.35696-1-yuka@yuka.dev> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 = sizeof(map_info); + __u32 map_flags_for_check = map->def.map_flags; int err; memset(&map_info, 0, map_info_len); @@ -5093,11 +5094,20 @@ static bool map_is_reuse_compat(const struct bpf_map *map, int map_fd) return false; } + /* 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 == BPF_MAP_TYPE_DEVMAP || map->def.type == BPF_MAP_TYPE_DEVMAP_HASH) + map_flags_for_check |= BPF_F_RDONLY_PROG; + return (map_info.type == map->def.type && map_info.key_size == map->def.key_size && map_info.value_size == map->def.value_size && map_info.max_entries == map->def.max_entries && - map_info.map_flags == map->def.map_flags && + map_info.map_flags == map_flags_for_check && map_info.map_extra == map->map_extra); } -- 2.50.1