From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-179.mta0.migadu.com (out-179.mta0.migadu.com [91.218.175.179]) (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 A700F3672B8 for ; Tue, 26 May 2026 02:56:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779764177; cv=none; b=EazlEzvC5O3iOoKvoTYCpJUpFeyXnXRlExiNyZNLWHqJovxZCg1LUD5xlgSuu4gAJvZwkE+2+8cQWmsQdu0+BisjEMz2KuaSQp1ZyAOOXJXJkAt4JHYFtBpmG/goatm/N9OwO7657ZZL0Lh96Ex++MeghvV9eA0TcAesdT+vyPE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779764177; c=relaxed/simple; bh=Qb34UP3m6VO0wh6Lgjx+hU31ESJhtEJZME2tcN4Tr6w=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=aIbTmnr8mpT155NVgN2Ce+87vhv2I9F1IVjnsgVwsCV619pltmiX6dBo5CM6cTuKhxZ+PC9zXA/r90L5ljDjppGgbciAOr95RaLBZVs85GXRQhURk6U1aJMCZlCGO+GY8MSg/8vh14qv5Jm3k2OZMKSx9yxclnsFxX+gyGB9pBA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=iwgOfM1h; arc=none smtp.client-ip=91.218.175.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="iwgOfM1h" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1779764172; 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=X1djAiNq52G6WM13xP8X19UCENtmyTYi9Go8YgiXomE=; b=iwgOfM1hJ5jpeExJVBJzO6lAXYq4AnW3L1FuaahjS+fJkdwHq6bn4ScTw4ysXfP/fyVZm0 Ugl9bKZLLVWTDRazYC171U7Xwk11Mb+0ASfcUcDXqyamJ6szsQBVR42zZgpNJI1R5GMkzO NqZUL+zyYPrmbIkIAC+hH/fUoBTVPTQ= From: Jiayuan Chen To: netdev@vger.kernel.org Cc: daniel@iogearbox.net, kuba@kernel.org, ast@kernel.org, martin.lau@linux.dev Subject: [PATCH net-next v2] net/sched: cls_bpf: prevent unbounded recursion in offload rollback Date: Tue, 26 May 2026 10:55:29 +0800 Message-ID: <20260526025529.24382-1-jiayuan.chen@linux.dev> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Quan Sun reported [1] a stack overflow in cls_bpf_offload_cmd(). Reproducer on netdevsim: add a skip_sw cls_bpf filter, set the bpf_tc_accept debugfs knob to 0, then `tc filter replace`. The replace calls tc_setup_cb_replace() which fails. cls_bpf_offload_cmd() then swaps prog/oldprog and recursively calls itself to roll back. But bpf_tc_accept=0 makes the rollback fail too, which triggers yet another rollback frame with the same arguments, and so on until the stack is exhausted. bpf_tc_accept is just a convenient knob for the reproducer. Any driver whose tc_setup_cb_replace() fails twice in a row can hit the same loop, so this is not a netdevsim-only issue. Two ways to fix it: 1) Have the rollback call tc_setup_cb_add() on oldprog instead of re-entering cls_bpf_offload_cmd(). 2) Mark the rollback frame with a flag and skip a second-level rollback from inside it. Go with (2). It is the smaller change and keeps the original behaviour: the rollback still goes through tc_setup_cb_replace(), so the driver gets one real chance to restore its state. If that attempt also fails, we just return the original error instead of recursing. [1]: https://lore.kernel.org/bpf/ce5a6005-3c5e-4696-9e05-eba9461dc860@std.uestc.edu.cn/T/#u Fixes: 102740bd9436 ("cls_bpf: fix offload assumptions after callback conversion") Reviewed-by: Jakub Kicinski Signed-off-by: Jiayuan Chen --- v1 -> v2: Target net-next instead of bpf and, plus a few small changes. v1: https://lore.kernel.org/bpf/20260522025854.341647-1-jiayuan.chen@linux.dev/ --- net/sched/cls_bpf.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c index 9a346b6221b35..001d8c4ebfedc 100644 --- a/net/sched/cls_bpf.c +++ b/net/sched/cls_bpf.c @@ -142,7 +142,8 @@ static bool cls_bpf_is_ebpf(const struct cls_bpf_prog *prog) static int cls_bpf_offload_cmd(struct tcf_proto *tp, struct cls_bpf_prog *prog, struct cls_bpf_prog *oldprog, - struct netlink_ext_ack *extack) + struct netlink_ext_ack *extack, + bool is_rollback) { struct tcf_block *block = tp->chain->block; struct tc_cls_bpf_offload cls_bpf = {}; @@ -177,7 +178,8 @@ static int cls_bpf_offload_cmd(struct tcf_proto *tp, struct cls_bpf_prog *prog, &oldprog->in_hw_count, true); if (prog && err) { - cls_bpf_offload_cmd(tp, oldprog, prog, extack); + if (!is_rollback) + cls_bpf_offload_cmd(tp, oldprog, prog, extack, true); return err; } @@ -208,7 +210,7 @@ static int cls_bpf_offload(struct tcf_proto *tp, struct cls_bpf_prog *prog, if (!prog && !oldprog) return 0; - return cls_bpf_offload_cmd(tp, prog, oldprog, extack); + return cls_bpf_offload_cmd(tp, prog, oldprog, extack, false); } static void cls_bpf_stop_offload(struct tcf_proto *tp, @@ -217,7 +219,7 @@ static void cls_bpf_stop_offload(struct tcf_proto *tp, { int err; - err = cls_bpf_offload_cmd(tp, NULL, prog, extack); + err = cls_bpf_offload_cmd(tp, NULL, prog, extack, false); if (err) pr_err("Stopping hardware offload failed: %d\n", err); } -- 2.43.0