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 22F4346D082; Tue, 21 Jul 2026 17:49:27 +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=1784656169; cv=none; b=AEYwjGV/B9wjIoXu+0HUmtjZ99rGa2kDaxVwL8chQon1g8Rn83D7e0yQ+Lut3WrfMIOkJhWSmP2GFQTpPLRw4s4VGJdAec8q7gbeS1hloonc8leja3StwrqTqHBAf4KeTnceuB1rjVPbdlFf00Y8MTcD6abuYJuFmxA/o/uwa6Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784656169; c=relaxed/simple; bh=6MmocA0Dk2KPoQ90CWFV2r4FuoWdZ7BnhKnrIMjVwZI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HKTGJQxbVH0E+QVZEBujICcW52SY5Eh/W3iZOEg3bL0qBmwAZcIDvXhoqo1lCEQwVgv1iwQi9SCTOlFh8L36ISE6lqCBwS/mvpTqcUHaNrs36g9Ten6nEr8ZIxbyZND3Afbc9AmOsqHVtY+8nWwBRE39OOX4EmmukrsrPWS+5JI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ETRkMPyN; 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="ETRkMPyN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 47D061F00A3F; Tue, 21 Jul 2026 17:49:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784656167; bh=nJmqb1FZQSJ+wEgv3vKwr44BRKAHY6bakFTQ6lw+v94=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ETRkMPyNfvE8OBwvYAgYbt/7ekjiy573Bz4RhQJ4sawcbaXH95ZvPdm15qYvU9wBG 053FIXD/4qzRGJf0e4LY/snLcieDnqqv+YgYTKeYPdkz7jvA1jnNsQrfu1/0QWpXa8 OKNayAX7eMw692wH0TSkthWa4xYjRZu8/1blwWhU= 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 6.18 0242/1611] net/sched: cls_bpf: prevent unbounded recursion in offload rollback Date: Tue, 21 Jul 2026 17:05:58 +0200 Message-ID: <20260721152520.461593758@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152514.750365251@linuxfoundation.org> References: <20260721152514.750365251@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 6.18-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