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Wed, 11 Nov 2026 05:27:22 -0800 (PST) Received: from localhost.localdomain ([98.148.34.5]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1b3b5890c0esm16146038c88.1.2026.11.11.05.27.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Nov 2026 05:27:21 -0800 (PST) From: Hungyu Lin To: giometti@enneenne.com Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, dennylin0707@gmail.com Subject: [PATCH v2] pps: reject N_PPS on pseudo-terminals Date: Wed, 11 Nov 2026 13:27:09 +0000 Message-ID: <20261111132709.5959-1-dennylin0707@gmail.com> X-Mailer: git-send-email 2.43.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Attaching N_PPS to a PTY registers a PPS source even though PTYs do not report DCD changes. An unprivileged user can exhaust the PPS source IDs this way, causing registration of a real PPS source to fail with -EBUSY. Reject N_PPS on PTYs before allocating a source. Fixes: a0880df0ccde ("pps: serial clients support") Suggested-by: Rodolfo Giometti Signed-off-by: Hungyu Lin --- Changes in v2: - Reject PTYs before registering a PPS source, as suggested by Rodolfo. - Drop the stable Cc. v1: https://lore.kernel.org/r/20261107211753.75932-1-dennylin0707@gmail.com drivers/pps/clients/pps-ldisc.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/pps/clients/pps-ldisc.c b/drivers/pps/clients/pps-ldisc.c index fa5660f3c4b7..83f4caced0c9 100644 --- a/drivers/pps/clients/pps-ldisc.c +++ b/drivers/pps/clients/pps-ldisc.c @@ -46,6 +46,9 @@ static int pps_tty_open(struct tty_struct *tty) struct pps_device *pps; int ret; + if (drv->type == TTY_DRIVER_TYPE_PTY) + return -EINVAL; + info.owner = THIS_MODULE; info.dev = NULL; snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index); -- 2.50.1 (Apple Git-155)