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 0020B3EBF07 for ; Mon, 16 Feb 2026 20:15:22 +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=1771272924; cv=none; b=TDjCkpMjcL01yX3sYKr4uxGARqAsdx2XmptOMb7EEIJzUAz7VEW2dxaAYE/IXB3IfkF+QyiCf8RG3ZVy4HcH133OBAw9iogr124fKSVJKI8HIPai8Lrhy5eZFenQixtq2s7jO+VWUapkO8moxtFxS1wNfIIdaB0T9JPCUseks84= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771272924; c=relaxed/simple; bh=yHTub/6dAaEppxaLT/BoJuX2CsZN5Kva6LgQBUw/3UY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Z1WkQsEjNVp4Un3hu49r2/ynenrknuBMw4PDgZ8EUflaps/pynGESQvlOIiCsu3J6KT+QriHVuJZthDkKLNfhkIibRk25V3fXBp92WelNE1yVRSTyrkdNfV8HDJVcRI4NNM1NEmWlGfcHm94WM9BK7uwy8kSkQ5Ke/EQ7TEbfsY= 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=giXTq+6l; 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="giXTq+6l" Received: from ms-a2 (211.4.31.150.dy.iij4u.or.jp [150.31.4.211]) (authenticated bits=0) by www2881.sakura.ne.jp (8.16.1/8.16.1) with ESMTPSA id 61GKETWq039148 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Tue, 17 Feb 2026 05:14:29 +0900 (JST) (envelope-from kohei@enjuk.jp) DKIM-Signature: a=rsa-sha256; bh=W8IeNTYHbP+UZ6w1LZGRpiOEWQPTM5igsV4ZklRjJo0=; c=relaxed/relaxed; d=enjuk.jp; h=From:To:Subject:Date:Message-ID; s=rs20251215; t=1771272870; v=1; b=giXTq+6lC392xS8Tuyu9eFxsSOYzlbx15Ey56klUB/S3TAZRoak29AuiwGidYwP5 3GbE6RQPTQ/Tyh/jAXvupNtup3s+X4VjCTXGstwMwtVsoDkAzzQusnjbGd5dgWXk hpvZw5qZZpmaRHf8PBBHgzgypOLz7RDVzC8rabLlFsIO4R2Ib9BNjPqo0Q2cpEdU 7mTAS/A7VUFjMNoRKc1pQjUazPpbAi3rfOFbRGaGBBbeSNuZlPpcivjioW+3E9mB XBQksoVntObcey5L0ZN+btyHHq7knlg5Sj7HbZ6/xaNOpgAU3Wgqph8NpKggqZ81 eR5zA32/pFiWZR5pHXhWSQ== 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 , kohei.enju@gmail.com, Kohei Enju , syzbot+10cc7f13760b31bd2e61@syzkaller.appspotmail.com Subject: [PATCH v1 bpf] bpf: devmap: fix stack-out-of-bounds write in get_upper_ifindexes() Date: Mon, 16 Feb 2026 20:13:07 +0000 Message-ID: <20260216201428.65641-1-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 --- kernel/bpf/devmap.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c index 2625601de76e..cdc4299a5955 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 +617,9 @@ 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 +737,9 @@ 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