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[174.29.1.49]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-70188bd9ecdsm525519eaf.2.2026.10.15.16.33.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Oct 2026 16:33:44 -0700 (PDT) From: James Hilliard Date: Thu, 15 Oct 2026 17:33:34 -0600 Subject: [PATCH net v4 4/5] ptp: vclock: serialize extended samples with counter updates Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261015-ptp-vclock-sampling-v4-4-cba6ffc8ceb6@gmail.com> References: <20261015-ptp-vclock-sampling-v4-0-cba6ffc8ceb6@gmail.com> In-Reply-To: <20261015-ptp-vclock-sampling-v4-0-cba6ffc8ceb6@gmail.com> To: netdev@vger.kernel.org, Paolo Abeni , Jakub Kicinski , Richard Cochran , Andrew Lunn , Yangbo Lu , Miroslav Lichvar Cc: Eric Dumazet , "David S. Miller" , linux-kernel@vger.kernel.org, Vadim Fedorenko , James Hilliard X-Mailer: b4 0.15.2 The extended and cross-timestamp callbacks sample the physical clock before taking the virtual clock mutex. A concurrent frequency adjustment can advance the timecounter and change its multiplier in between, so the older sample is converted using a different frequency than the one in effect when it was taken. Take the mutex before sampling and keep it held through the conversion. Retain timecounter_cyc2time() and its existing conversion window. A PHC sample need not advance the counter: for example, e1000e explicitly allows non-monotonic SYSTIM readings. Treating a slightly older sample as a forward delta would instead advance virtual time by nearly a full counter wrap. This race was found by code inspection of the virtual clock sampling paths. Fixes: f0067ebfc42b ("ptp: add gettimex64() to virtual clocks.") Fixes: 21fad63084c2 ("ptp: add getcrosststamp() to virtual clocks.") Signed-off-by: James Hilliard --- drivers/ptp/ptp_vclock.c | 32 ++++++++++++++------------------ 1 file changed, 14 insertions(+), 18 deletions(-) diff --git a/drivers/ptp/ptp_vclock.c b/drivers/ptp/ptp_vclock.c index 5f49f81891ef..88161be5eabc 100644 --- a/drivers/ptp/ptp_vclock.c +++ b/drivers/ptp/ptp_vclock.c @@ -115,20 +115,18 @@ static int ptp_vclock_gettimex(struct ptp_clock_info *ptp, struct ptp_clock *pptp = vclock->pclock; struct timespec64 pts; int err; - u64 ns; - - err = pptp->info->getcyclesx64(pptp->info, &pts, sts); - if (err) - return err; if (mutex_lock_interruptible(&vclock->lock)) return -EINTR; - ns = timecounter_cyc2time(&vclock->tc, timespec64_to_ns(&pts)); - mutex_unlock(&vclock->lock); + err = pptp->info->getcyclesx64(pptp->info, &pts, sts); + if (!err) { + u64 ns = timecounter_cyc2time(&vclock->tc, timespec64_to_ns(&pts)); - *ts = ns_to_timespec64(ns); + *ts = ns_to_timespec64(ns); + } + mutex_unlock(&vclock->lock); - return 0; + return err; } static int ptp_vclock_settime(struct ptp_clock_info *ptp, @@ -154,20 +152,18 @@ static int ptp_vclock_getcrosststamp(struct ptp_clock_info *ptp, struct ptp_vclock *vclock = info_to_vclock(ptp); struct ptp_clock *pptp = vclock->pclock; int err; - u64 ns; - - err = pptp->info->getcrosscycles(pptp->info, xtstamp); - if (err) - return err; if (mutex_lock_interruptible(&vclock->lock)) return -EINTR; - ns = timecounter_cyc2time(&vclock->tc, ktime_to_ns(xtstamp->device)); - mutex_unlock(&vclock->lock); + err = pptp->info->getcrosscycles(pptp->info, xtstamp); + if (!err) { + u64 ns = timecounter_cyc2time(&vclock->tc, ktime_to_ns(xtstamp->device)); - xtstamp->device = ns_to_ktime(ns); + xtstamp->device = ns_to_ktime(ns); + } + mutex_unlock(&vclock->lock); - return 0; + return err; } static long ptp_vclock_refresh(struct ptp_clock_info *ptp) -- 2.53.0