From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from www2881.sakura.ne.jp (www2881.sakura.ne.jp [49.212.198.91]) (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 1518136605C for ; Fri, 20 Feb 2026 19:31:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=49.212.198.91 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771615905; cv=none; b=tNBictvOhzpfWNkrq49U3oH6Zg4M8r7kZtblaM/s3eu9DW8Vkokow5a/rZzR9gR2IXXMNmPoCdpyQoLtpfdSTUDAHfUCFpOaId29jll+8ulqlypPVtV5jNtztkelVuatYAoiGPTTMUn9tgSxjWFufBUnDE9XE/rNfWRnXeOhtOo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771615905; c=relaxed/simple; bh=2zlgzy8tMLgAVXnkhjww6tl7qwzbhqNbvtglCF+jBTo=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=m8wOxl7jpcXx2WKZbR7Cv6ux8/hibmHL0kdLNK9rbn7jmFOXqGx1nJCdYTERVxlysK8feiCD5yze5ID4xpfRQeqjhbpmXSeKU7WeyX6Q94Dy5M7xGoIG6Q09oZTbGzcbgLBy0Pi3Rl1oFwk40DBoCRKCFZ1CNHnD1nQw63iNwPs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=enjuk.jp; spf=pass smtp.mailfrom=enjuk.jp; dkim=pass (2048-bit key) header.d=enjuk.jp header.i=@enjuk.jp header.b=dntj9rys; arc=none smtp.client-ip=49.212.198.91 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=enjuk.jp Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=enjuk.jp Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=enjuk.jp header.i=@enjuk.jp header.b="dntj9rys" Received: from ms-a2 (54.52.30.125.dy.iij4u.or.jp [125.30.52.54]) (authenticated bits=0) by www2881.sakura.ne.jp (8.16.1/8.16.1) with ESMTPSA id 61KJUpva004592 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Sat, 21 Feb 2026 04:30:51 +0900 (JST) (envelope-from kohei@enjuk.jp) DKIM-Signature: a=rsa-sha256; bh=8g8OID58uVFy8gevFzmKG0HT71La/krGCOGvXbey9UI=; c=relaxed/relaxed; d=enjuk.jp; h=From:To:Subject:Date:Message-ID; s=rs20251215; t=1771615851; v=1; b=dntj9rysRXD8nkifW7mP7edJpQr7UVzuB+6C/AnAlfrHQGQPlGt//GrSKEZO/6nt lkgFeufqrKY4/5fDpUKlrDQiPqy51fJMumdkIACeiumoo3HtyoTCEgHeh9PEtsEm GLhCtxu6z/nByhkhDMkIYC6Mf9xOxuNIr5iBOYpoXEoudU5Yy98PDFhL6Vb4AKCk 8+z5IQlLpF6Vp8dPSWBy0OMLDvPXeSOZZcyjCIZF62ATWTUDV0OnaELvNgczc64V PS+oR+Y+6VFg5vQ6csCvQ+kXFgQjiBQyJR4zLu+9IO8tFvFNHcZfE3xAwGSgFpOq iijGeHKmFunXI6J9yF+XzA== From: Kohei Enju To: netdev@vger.kernel.org, bpf@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , "David S. Miller" , Jakub Kicinski , Jesper Dangaard Brouer , John Fastabend , Stanislav Fomichev , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Hao Luo , Jiri Olsa , Jussi Maki , =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= , kohei.enju@gmail.com, Kohei Enju , syzbot+10cc7f13760b31bd2e61@syzkaller.appspotmail.com Subject: [PATCH v2 bpf] bpf: devmap: fix stack-out-of-bounds write in get_upper_ifindexes() Date: Fri, 20 Feb 2026 19:29:45 +0000 Message-ID: <20260220193039.7129-1-kohei@enjuk.jp> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit get_upper_ifindexes() iterates over all upper devices and writes their indices into an array without checking bounds. Also the callers assume that the max number of upper devices is MAX_NEST_DEV and allocate excluded_devices[1+MAX_NEST_DEV] on the stack, but that assumption is not correct and the number of upper devices could be larger than MAX_NEST_DEV (e.g., many macvlans), causing a stack-out-of-bounds write. Add a max parameter to get_upper_ifindexes() to avoid the issue. To reproduce, create more than MAX_NEST_DEV(8) macvlans on a device with an XDP program attached using BPF_F_BROADCAST | BPF_F_EXCLUDE_INGRESS. Then send a packet to the device to trigger the XDP redirect path. Reported-by: syzbot+10cc7f13760b31bd2e61@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/698c4ce3.050a0220.340abe.000b.GAE@google.com/T/ Fixes: aeea1b86f936 ("bpf, devmap: Exclude XDP broadcast to master device") Signed-off-by: Kohei Enju --- Changes: v2: - fix formatting, accounting that max-line-length is 100 v1: https://lore.kernel.org/bpf/20260216201428.65641-1-kohei@enjuk.jp/ --- kernel/bpf/devmap.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c index 2625601de76e..c8c49d86a403 100644 --- a/kernel/bpf/devmap.c +++ b/kernel/bpf/devmap.c @@ -588,16 +588,18 @@ static inline bool is_ifindex_excluded(int *excluded, int num_excluded, int ifin } /* Get ifindex of each upper device. 'indexes' must be able to hold at - * least MAX_NEST_DEV elements. + * least 'max' elements. * Returns the number of ifindexes added. */ -static int get_upper_ifindexes(struct net_device *dev, int *indexes) +static int get_upper_ifindexes(struct net_device *dev, int *indexes, int max) { struct net_device *upper; struct list_head *iter; int n = 0; netdev_for_each_upper_dev_rcu(dev, upper, iter) { + if (n >= max) + break; indexes[n++] = upper->ifindex; } return n; @@ -615,7 +617,8 @@ int dev_map_enqueue_multi(struct xdp_frame *xdpf, struct net_device *dev_rx, int err; if (exclude_ingress) { - num_excluded = get_upper_ifindexes(dev_rx, excluded_devices); + num_excluded = get_upper_ifindexes(dev_rx, excluded_devices, + ARRAY_SIZE(excluded_devices) - 1); excluded_devices[num_excluded++] = dev_rx->ifindex; } @@ -733,7 +736,8 @@ int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb, int err; if (exclude_ingress) { - num_excluded = get_upper_ifindexes(dev, excluded_devices); + num_excluded = get_upper_ifindexes(dev, excluded_devices, + ARRAY_SIZE(excluded_devices) - 1); excluded_devices[num_excluded++] = dev->ifindex; } -- 2.51.0