hwmon: (coretemp) Fix 32-bit jiffies wraparound in show_temp()

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 <sashiko-bot@kernel.org>
Fixes: bebe467823c0 ("hwmon: New coretemp driver")
Cc: stable@vger.kernel.org
Tested-by: Asaf Nuri Bertizlioğlu <ycistak@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

0 files changed, 0 insertions, 0 deletions