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 8F39B3A2E12; Sat, 12 Sep 2026 20:03:44 +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=1789243425; cv=none; b=pkLQFYd0iZ7OWEzd16j0HXldZZo1EBSDYBrJGeqqNljZ80CYQzFAZvFKn33KqiJzGtL4ENNLrvw0Th7YshgJA7TxgGfMxxmoF1jUWiogRkb97GMwPhvnKCcmbJu+3v3N6B+eptugVTzPzxhNS+yeM9en/QqSkAIDbL0jB5EMUPE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789243425; c=relaxed/simple; bh=/A+g+NSZWkTA08KSWP8dAh4ZSe3fYZTu0UKe4xhX5m0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NviciMefdfTFgZc/GFzFywMh578KrTg3sD3eyiq5Cu1Yw87Wte7RA+bLGhcwYjzrBmKN3plozcomi2u2++RuKIRKvu7HkoLTuCEoUT3gHMI4stIGXzLdrxXN3Q+Dpiw8jedaesNdGmmG2/AZtZhX7M54NrPOmgc0jw5SyZZiZTQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=joqkGlsD; 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="joqkGlsD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E97011F000FF; Sat, 12 Sep 2026 20:03:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789243424; bh=7FI/DaoBFnKJz8BFhLufHBr3vUYdkCeLEOV9+Mj7Zr0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=joqkGlsDVPuc/SWvqflO3KffWlv2npiVniiMkbPBeLCjkynhMyNoocmlyqd1DmnB7 f8FmIO3FyvvZy68/XQ2ZlQMh9eHflOrFmgG6R+Q7lnK5gKha6lLILfbZkR6j0ULZxf ctTDzkWil4xOn0H868iPiGS6RouLgdSxB7qdaKPU= 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 5.10 752/798] Bluetooth: RFCOMM: Validate MTU in rfcomm_apply_pn() to prevent infinite loop Date: Sat, 12 Sep 2026 09:06:20 +0200 Message-ID: <20260912065534.303951632@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260912065516.948645775@linuxfoundation.org> References: <20260912065516.948645775@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 5.10-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 4d3a8c8ba512c..828c18d91e829 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