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 40DA537FF60; Sat, 12 Sep 2026 19:15:03 +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=1789240504; cv=none; b=Ei9CvlLUqOq3tNmxcGwBz6Cx+WCUxFJ+APJ8+CXzeMZ5Z0FdUNbUNdbXBrK8f9TezZxG/QmsZpPG+PX5D3hAvZlmyo4KQfYzSMAqzttSa+KSLph9CfN2vyB+p2jZvGaEMTblLVAGoedvWjXx/CVKiYLykcTZ/mNY0iFo5hx0sc0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789240504; c=relaxed/simple; bh=dE9IRv6GVtdwmc6QDQNqAkEhBijEOjIpuMKbbtSWaKk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rkhhVjS5/JbhBZlWr26KlGQcjYheKnV+4Fh2NiagQbASF5zQKHTHlkbNNzm849qJaV0ZoiciDzwhQ2QiXMLeMkvDRsSNy3etXqKpdUNa+iiIcXq7Y/MX1kMVA19MjdcdqibLwZA3O/XKIdT14F+QcuWAO8s+tiJW8bVy7yg2+0k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=K0yjFOE9; 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="K0yjFOE9" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 462EE1F000FF; Sat, 12 Sep 2026 19:15:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789240503; bh=9QJJkTI+mf9zMUGgLehvkx/MRekGyJLbRWvjOdbGrNg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=K0yjFOE97lB3rQQbkt4KBg64PFeprqD4O0LeFFK9+/g3Xl83SU8bpZu4z0aYiluv9 NGWXgNC5YTxlmiWYDwsa5lEmar/YCCuXQSFOWcR0etm0BHoA2hoM6amJIZBFuu7Bzr OAplkSEBTdTvDIpWXPUpIEnEZ9IHhXCFR0zy3Lx8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Hyunwoo Kim , Luiz Augusto von Dentz , Sasha Levin Subject: [PATCH 5.15 882/935] Bluetooth: RFCOMM: Validate MTU in rfcomm_apply_pn() to prevent infinite loop Date: Sat, 12 Sep 2026 09:05:12 +0200 Message-ID: <20260912065547.043696902@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065526.833703348@linuxfoundation.org> References: <20260912065526.833703348@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 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Hyunwoo Kim [ Upstream commit 44c98fd082eafd49d55a8a4077ff488175b2fe24 ] rfcomm_apply_pn() accepts the MTU value from a remote PN (Parameter Negotiation) frame without checking for zero. When the remote peer sends an MTU of zero, d->mtu is set to 0. This causes the sendmsg path to enter an infinite loop when fragmenting data, as each fragment has size == min_t(size_t, len, 0) == 0, so the remaining length never decreases. The infinite allocation of zero-length skbs exhausts all system memory. Fix by clamping d->mtu to RFCOMM_DEFAULT_MTU when the negotiated value is zero, consistent with the initial value assigned in rfcomm_dlc_alloc(). Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Hyunwoo Kim Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin --- net/bluetooth/rfcomm/core.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/bluetooth/rfcomm/core.c b/net/bluetooth/rfcomm/core.c index 349f62a18190e..2914ac1c50024 100644 --- a/net/bluetooth/rfcomm/core.c +++ b/net/bluetooth/rfcomm/core.c @@ -1454,6 +1454,10 @@ static int rfcomm_apply_pn(struct rfcomm_dlc *d, int cr, struct rfcomm_pn *pn) d->mtu = __le16_to_cpu(pn->mtu); + /* MTU 0 causes an infinite loop when fragmenting in sendmsg */ + if (!d->mtu) + d->mtu = RFCOMM_DEFAULT_MTU; + if (cr && d->mtu > s->mtu) d->mtu = s->mtu; -- 2.53.0