From 9a6aa085c94c7f2817c4d50a7264e6fb51286f40 Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Sat, 31 Oct 2026 03:09:14 +0000 Subject: [PATCH] hwmon: (coretemp) Fix 32-bit jiffies wraparound in show_temp() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit show_temp() rate-limits MSR reads by storing tdata->last_updated as an unsigned long and comparing it against jiffies using time_after(jiffies, tdata->last_updated + HZ). time_after() relies on signed long subtraction, which only produces the expected result while the two timestamps are within LONG_MAX jiffies of each other. On 32-bit kernels, if tempX_input is not read for more than LONG_MAX jiffies (~24.85 days at HZ=1000), the signed difference flips sign and time_after() evaluates to false. Because tdata->last_updated is only refreshed when time_after() succeeds, subsequent reads remain blocked from refreshing for another ~24.85 days until jiffies wraps past tdata->last_updated + HZ again, returning either a stale cached temperature or -ENODATA if the sensor had never been read since initialization. Store tdata->last_updated as a u64 and use get_jiffies_64() with time_after64(), which does not wrap in any practical uptime. Reported-by: Sashiko Fixes: bebe467823c0 ("hwmon: New coretemp driver") Cc: stable@vger.kernel.org Tested-by: Asaf Nuri Bertizlioğlu Signed-off-by: Guenter Roeck --- drivers/hwmon/coretemp.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c index 7fced0e2abeb..96d57fe12de6 100644 --- a/drivers/hwmon/coretemp.c +++ b/drivers/hwmon/coretemp.c @@ -76,7 +76,7 @@ struct temp_data { int temp; bool temp_valid; int tjmax; - unsigned long last_updated; + u64 last_updated; unsigned int cpu; int index; u32 cpu_core_id; @@ -407,7 +407,7 @@ static ssize_t show_temp(struct device *dev, mutex_lock(&tdata->update_lock); /* Check whether the time interval has elapsed */ - if (time_after(jiffies, tdata->last_updated + HZ)) { + if (time_after64(get_jiffies_64(), tdata->last_updated + HZ)) { tjmax = get_tjmax(tdata, dev); rdmsrq_on_cpu(tdata->cpu, tdata->status_reg, &val.q); /* @@ -417,7 +417,7 @@ static ssize_t show_temp(struct device *dev, */ tdata->temp_valid = (val.l >> 31) & 1; tdata->temp = tjmax - ((val.l >> 16) & 0xff) * 1000; - tdata->last_updated = jiffies; + tdata->last_updated = get_jiffies_64(); } valid = tdata->temp_valid; @@ -521,11 +521,8 @@ init_temp_data(struct platform_data *pdata, unsigned int cpu, int pkg_flag) tdata->cpu = cpu; tdata->cpu_core_id = topology_core_id(cpu); tdata->attr_size = MAX_CORE_ATTRS; - /* - * A zero timestamp does not look stale on 32-bit, where jiffies - * starts just short of wrapping. Backdate it instead. - */ - tdata->last_updated = jiffies - HZ - 1; + /* Backdate to force a refresh on the first read */ + tdata->last_updated = get_jiffies_64() - HZ - 1; mutex_init(&tdata->update_lock); return tdata; }