From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 6D35F46EC9B; Tue, 21 Jul 2026 19:22:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784661732; cv=none; b=DDLkq1ER+3lZiFPx8M0CkMIgBGaplgriN/Kd0roT+Objzp14ZK/+OlR8fm5Ag8h+led9eHVU29P6LjucYwCSJPTTz5Yp62oSkUo7cwWt5WxVQwKvq/T1lal98XDdebquQkNPP/V/caIMKzzM098kWUXm4ne/lzJYXEY6OUIsvZE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784661732; c=relaxed/simple; bh=+yzHlCnjAFh+rB3quGUxXw4I9Ho/p1sfZwQ4y7ZQBIY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=LQdg/vFBti5DaBWXfrF9m1SXkT4vDtfgL4RLYeI0f/UA9ORwGuj6xOcZoUEpAm5mPPCCOUQl/7b7xSgZTKSonHxlIU6DINYCIgxtcrOsdY9t7Wk50trHednpvdZ5TiZJ5NpI6x7GvtPFv1xhOpBHlIwoPkQWJ3aD2i+eL+eHnXU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=bp+hg1V4; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="bp+hg1V4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D27491F00A3A; Tue, 21 Jul 2026 19:22:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784661731; bh=V2YydgXdBItqyfaNWhZnwXAHdb+bC4adBbv0szJ8Y84=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=bp+hg1V4B+7AwaB4FWMj8W5QxjhoXm/py8sj58fHPuZIu4aUIqGbgN9RsBGYlr6wK +JNM7ocjMSvH9Tdgta8KT2O3DOxWBqp50I+ktkAGz1o7tCvkaHUL26KaRyOTyKK/Zy qQulWtbeTBKFEhoCkxLD2kM3AqpPummNPwlHCAfc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jakub Kicinski , Jiayuan Chen , Sasha Levin Subject: [PATCH 6.12 0175/1276] net/sched: cls_bpf: prevent unbounded recursion in offload rollback Date: Tue, 21 Jul 2026 17:10:18 +0200 Message-ID: <20260721152450.012575898@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152446.065700225@linuxfoundation.org> References: <20260721152446.065700225@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jiayuan Chen [ Upstream commit 27db54b90bcc7c37867fe664107fa25ea6a116e4 ] 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 Link: https://patch.msgid.link/20260526025529.24382-1-jiayuan.chen@linux.dev Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- 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 a32754a2658bb7..e888d0aa9f21a0 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); } -- 2.53.0