From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4B27A1E9B1A; Wed, 28 Jan 2026 15:31:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769614300; cv=none; b=UY225p8RYOe5rz39Ji21peNPibJes4u/byPaNTmY0okHCgHzGLUYEXzP2Hp5i5cVoTwh9OqsbR/KgZf2XXeXvoWutIV0vswJc2oSDAJIyrxUhkzqEdf+1OIBZsvIrneYoP4nvuUZue3hGOD2Tnj1XRErHVTODHN1mtGTmNPoMfk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769614300; c=relaxed/simple; bh=SDdG2h+/5V1hhoxgFB7bNd9VzTXBj/BbMuxm6FD3fCE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=UYFJTTMMHS70t5QZu/As4vbmJvP9ohtwIzYaCthgcVblHRTY6Gn8sUEvI7PhpYxLWpxn7W/HfluZKnjdBB1L7Ho95wmjhb6YLRm8cHDOscp+SaWrXYUjCswiR/qYHD+LmxoKreZSHaDLVCsEOkZqlzDVl39NuidtueuwBEucYsg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gI1JI5EE; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="gI1JI5EE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A14DDC4CEF7; Wed, 28 Jan 2026 15:31:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1769614300; bh=SDdG2h+/5V1hhoxgFB7bNd9VzTXBj/BbMuxm6FD3fCE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gI1JI5EEj/o2y//Vl4o8HPtYBM+zYn6frMPQ+wzyRJVpCaDppumnICrOWq1vwb0QL /CY9SfuWkW5PLl/lGuNc1oDhzdZu/d/1AxJ4b9BkPzdO6xmqbHvJCs/qDp9Jf8xvlT GPn/au87nirsxwPZbB++tdQwUx923BlTfIuZbrzA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Richard Cochran , Vadim Fedorenko , Wojtek Wasko , Thomas Gleixner , "David S. Miller" , Sasha Levin Subject: [PATCH 6.6 094/254] ptp: Add PHC file mode checks. Allow RO adjtime() without FMODE_WRITE. Date: Wed, 28 Jan 2026 16:21:10 +0100 Message-ID: <20260128145348.210690269@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260128145344.698118637@linuxfoundation.org> References: <20260128145344.698118637@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wojtek Wasko [ Upstream commit b4e53b15c04e3852949003752f48f7a14ae39e86 ] Many devices implement highly accurate clocks, which the kernel manages as PTP Hardware Clocks (PHCs). Userspace applications rely on these clocks to timestamp events, trace workload execution, correlate timescales across devices, and keep various clocks in sync. The kernel’s current implementation of PTP clocks does not enforce file permissions checks for most device operations except for POSIX clock operations, where file mode is verified in the POSIX layer before forwarding the call to the PTP subsystem. Consequently, it is common practice to not give unprivileged userspace applications any access to PTP clocks whatsoever by giving the PTP chardevs 600 permissions. An example of users running into this limitation is documented in [1]. Additionally, POSIX layer requires WRITE permission even for readonly adjtime() calls which are used in PTP layer to return current frequency offset applied to the PHC. Add permission checks for functions that modify the state of a PTP device. Continue enforcing permission checks for POSIX clock operations (settime, adjtime) in the POSIX layer. Only require WRITE access for dynamic clocks adjtime() if any flags are set in the modes field. [1] https://lists.nwtime.org/sympa/arc/linuxptp-users/2024-01/msg00036.html Changes in v4: - Require FMODE_WRITE in ajtime() only for calls modifying the clock in any way. Acked-by: Richard Cochran Reviewed-by: Vadim Fedorenko Signed-off-by: Wojtek Wasko Reviewed-by: Thomas Gleixner Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- drivers/ptp/ptp_chardev.c | 16 ++++++++++++++++ kernel/time/posix-clock.c | 2 +- 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c index 6eecb53b3e670..1ed12e86ee000 100644 --- a/drivers/ptp/ptp_chardev.c +++ b/drivers/ptp/ptp_chardev.c @@ -153,6 +153,10 @@ long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd, case PTP_EXTTS_REQUEST: case PTP_EXTTS_REQUEST2: + if ((pccontext->fp->f_mode & FMODE_WRITE) == 0) { + err = -EACCES; + break; + } memset(&req, 0, sizeof(req)); if (copy_from_user(&req.extts, (void __user *)arg, @@ -194,6 +198,10 @@ long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd, case PTP_PEROUT_REQUEST: case PTP_PEROUT_REQUEST2: + if ((pccontext->fp->f_mode & FMODE_WRITE) == 0) { + err = -EACCES; + break; + } memset(&req, 0, sizeof(req)); if (copy_from_user(&req.perout, (void __user *)arg, @@ -262,6 +270,10 @@ long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd, case PTP_ENABLE_PPS: case PTP_ENABLE_PPS2: + if ((pccontext->fp->f_mode & FMODE_WRITE) == 0) { + err = -EACCES; + break; + } memset(&req, 0, sizeof(req)); if (!capable(CAP_SYS_TIME)) @@ -400,6 +412,10 @@ long ptp_ioctl(struct posix_clock_context *pccontext, unsigned int cmd, case PTP_PIN_SETFUNC: case PTP_PIN_SETFUNC2: + if ((pccontext->fp->f_mode & FMODE_WRITE) == 0) { + err = -EACCES; + break; + } if (copy_from_user(&pd, (void __user *)arg, sizeof(pd))) { err = -EFAULT; break; diff --git a/kernel/time/posix-clock.c b/kernel/time/posix-clock.c index b130bb56cc4e0..827abede72745 100644 --- a/kernel/time/posix-clock.c +++ b/kernel/time/posix-clock.c @@ -253,7 +253,7 @@ static int pc_clock_adjtime(clockid_t id, struct __kernel_timex *tx) if (err) return err; - if ((cd.fp->f_mode & FMODE_WRITE) == 0) { + if (tx->modes && (cd.fp->f_mode & FMODE_WRITE) == 0) { err = -EACCES; goto out; } -- 2.51.0