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Sat, 07 Nov 2026 13:26:14 -0800 (PST) Received: from localhost.localdomain ([98.148.34.5]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1b3755eb6efsm1146297c88.4.2026.11.07.13.26.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 07 Nov 2026 13:26:13 -0800 (PST) From: Hungyu Lin To: giometti@enneenne.com Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, dennylin0707@gmail.com Subject: [PATCH] pps: require CAP_SYS_TIME to attach N_PPS ldisc Date: Sat, 7 Nov 2026 21:17:53 +0000 Message-ID: <20261107211753.75932-1-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 Any unprivileged user can attach the N_PPS ldisc to a pty, and every attach registers a PPS source. At most PPS_MAX_SOURCES (256) sources can exist, so such a user can take all of them, after which registering a real PPS source fails with -EBUSY. Require CAP_SYS_TIME to attach N_PPS, the capability that PPS_SETPARAMS already needs to configure a source. Fixes: a0880df0ccde ("pps: serial clients support") Cc: stable@vger.kernel.org Signed-off-by: Hungyu Lin --- 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..54678f20edd5 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 (!capable(CAP_SYS_TIME)) + return -EPERM; + info.owner = THIS_MODULE; info.dev = NULL; snprintf(info.name, PPS_MAX_NAME_LEN, "%s%d", drv->driver_name, index); -- 2.43.0