From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f50.google.com (mail-wr1-f50.google.com [209.85.221.50]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 56CFC17DFE7 for ; Mon, 18 May 2026 01:00:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.50 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779066040; cv=none; b=pv0la+r+igLREJ/K9h38AGWeq68/868KEKC/52FEjPSWq8M4zyEMEELJHsMa7SoDZmvki9MYuwTG3P4+NDdO8Y2pwO7BAZtkWxJNzQdayvRh9YzoM3IDEMkaeKbMVCLfEpKRNety8SXHu/MUXGFHoIS6fxn5KppWceWE6Leh24I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779066040; c=relaxed/simple; bh=/PAGb0AvVuxMQZ9EWPg+15IzbZMM5u5h1WSSMcsAJIc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=G7VLowqthWsQLg1RzSLhqHIFdhDaY+/U5UaoCSebjlZrE02TM3hjbu8r5e1hZq+zV1ReHd1s5ljB90DPxF0DiT40Ohj+VDGDuliw8pVlCUcqDPTskvpXh0kZ9YB/fp1t2tZAHp2OTf4jBInM2VCVYvJlI9u1Dk9G/5YXag9jsc0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=T7MqMxRy; arc=none smtp.client-ip=209.85.221.50 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="T7MqMxRy" Received: by mail-wr1-f50.google.com with SMTP id ffacd0b85a97d-44ce78ab5feso1400316f8f.0 for ; Sun, 17 May 2026 18:00:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1779066038; x=1779670838; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=TpKkJC2kMiT9OA/pGYmBdZ/qheRDKlodtbgW4gbsoLY=; b=T7MqMxRyN3mtIW6mrZt+ka+DGksd+qTs78VrJd/WZoOKJZEFsXPhRTkXyYazSdPUc7 e66y9zgd+0HMEbSe1+buknqmv7MPpnbUrvvgNwSum4x15NgQ+8iP8gwBPePMmhz81zup J+zqXBeN49EF/gl/3/qVAuTzlES3RVRJNUmec03ovo6l3LiJvUhDh4Lximc8+KfMU8Or GFHRFY+ZFrZdHLDvTSZilPXaryCh+nF1vQemIpyAKEzDHcwb/HRCob8b2CwapWuGkBLI 1GLrudUzoMZzimwt94qIUsziws7bKEeD6EjsD5q5Cru7mLreJFb2iEOg8I8D1inxkyRi +/dw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779066038; x=1779670838; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=TpKkJC2kMiT9OA/pGYmBdZ/qheRDKlodtbgW4gbsoLY=; b=iXprzDoLuITYHkBA1U1WqgbFYrC7anRwzsF4SpeB5I1U4l1VKwPlj549DQzahN1wWZ +9O0XHMvxpM3azw3sNUALTTgUqUL21GdGLQcUYen9fwM2HxqiImrE0zrvgxbtq9wPXdf unLVfVpSUPWv1qUObrrqGkqdsB1647/zhmQNyM779naCx92fVIrZZ4Bym4WFKFsUwAHt k8SKMmXSxlxvY8Ed7UwfsZGM2OuqNWehpKacxnFC63sj4jE1gpn4BXGnhTlPhGVAvlPl kQJhHkuNfd8nGLsf5aX4aAasENPbNyG2eDtSUAy8GE+8iAszpgTagt8Bf01OhmwDifmI QHiA== X-Gm-Message-State: AOJu0YwljnK0rM56U/j3l1zyQ0oD0bWdPrCxkR6JWt2DguDmDW1kyawu 6HZ6nPJGwSKbpdKPbIhv7PCYCyBI6fG4qPC91siUzIj4N2E/yioHahuP X-Gm-Gg: Acq92OHYDOLwN56mjihqCCZ3/GjzT4vviHQ7ICzB3+UndaFqKfcb01+Ex4M67LhE9M8 ahMJ7EZvok3juKubIUsDbv8JqRCALKDfQGsUxFyrCyue3T20aHRMJj9Vc49gcT7KjWRR5XE3QXc /UWV/Bpnaa/GqbFkYLNT/WHlVlfg9FOITUEe9w5DCqFTKFRl3xnukRbWb4UAmtcobN7u1g5Ww82 D2As/ONdu44ZDwmk58Gt4E1skWrF+OjyGj/O/ibQLAMMhPJOzG+QTxKNeeqVyGIKOC4qC2sCh2n eqxFFg2R82PHcQUAqcrsQ2dR25A1lqVLfjWs0sPY/4WVj2WbMOH7xhO20eJbt0Y36bQNY1z98WH sZui9c5xdekd3ointn/OKJXuiMENtRQElkN7CJUUrS3+YmO3gAWarrGC2JwDT1StHVbbVEtveKh rmYSJdlXHhkEfbp8SfjATRU0+5Cw9kqPbjSgZqvV8FGDRdbsxzdaK8BIhrHAZ0lYMct340K4Uo/ A== X-Received: by 2002:a5d:5f47:0:b0:452:d03a:7abf with SMTP id ffacd0b85a97d-45e5c36bd31mr19056736f8f.15.1779066037595; Sun, 17 May 2026 18:00:37 -0700 (PDT) Received: from node ([202.47.63.86]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45d9adc2209sm30687972f8f.0.2026.05.17.18.00.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 17 May 2026 18:00:37 -0700 (PDT) From: Muhammad Bilal To: michael.bommarito@gmail.com Cc: linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org, marcel@holtmann.org, luiz.dentz@gmail.com, johan.hedberg@gmail.com Subject: Re: [PATCH] Bluetooth: L2CAP: rate-limit ECHO_RSP per signaling PDU Date: Sun, 17 May 2026 21:00:19 -0400 Message-ID: <20260518010019.121323-1-meatuni001@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260518002800.1361430-1-michael.bommarito@gmail.com> References: <20260518002800.1361430-1-michael.bommarito@gmail.com> Precedence: bulk X-Mailing-List: linux-bluetooth@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Michael, Thanks for the patch. The ECHO_REQ cap addresses one amplification vector, but the same N:1 amplification appears reachable via the unknown-command path in the same loop. When l2cap_bredr_sig_cmd() returns an error for an unrecognised command code, the loop calls l2cap_sig_send_rej() unconditionally: err = l2cap_bredr_sig_cmd(conn, cmd, len, skb->data); if (err) { BT_ERR("Wrong link type (%d)", err); l2cap_sig_send_rej(conn, cmd->ident); } A peer that packs N commands with an unknown code (e.g. 0xFF, len = 0) into a single signaling PDU would trigger N calls to l2cap_sig_send_rej(), sending N COMMAND_REJ responses, bypassing the new L2CAP_SIG_ECHO_BURST limit entirely. This produces the same TX queue saturation the patch intends to prevent, and also floods the kernel log with N BT_ERR() writes per PDU. A response counter covering all outbound responses generated per PDU would close both paths. Something like: int resp_count = 0; /* in the error path: */ if (err) { if (++resp_count <= L2CAP_SIG_ECHO_BURST) { BT_ERR("Wrong link type (%d)", err); l2cap_sig_send_rej(conn, cmd->ident); } continue; } /* existing echo path: */ if (cmd->code == L2CAP_ECHO_REQ && ++resp_count > L2CAP_SIG_ECHO_BURST) { skb_pull(skb, len); continue; } Using pr_warn_ratelimited() instead of BT_ERR() in the loop would also reduce log amplification independent of the skb path. Regards, Muhammad Bilal