timekeeping: Fix timex status validation for auxiliary clocks

The timekeeping_validate_timex() function validates the timex status
of an auxiliary system clock even when the status is not to be changed,
which causes unexpected errors for applications that make read-only
clock_adjtime() calls, or set some other timex fields, but without
clearing the status field.

Do the AUX-specific status validation only when the modes field contains
ADJ_STATUS, i.e. the application is actually trying to change the
status. This makes the AUX-specific clock_adjtime() behavior consistent
with CLOCK_REALTIME.

Fixes: 4eca49d0b621 ("timekeeping: Prepare do_adtimex() for auxiliary clocks")
Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260225085231.276751-1-mlichvar@redhat.com

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 91fa2003351c9dead5871962502156de17c85b25..c07e562ee4c1ad5cbbf505aee2afd4e17876faae 100644 (file)
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -2653,7 +2653,8 @@ static int timekeeping_validate_timex(const struct __kernel_timex *txc, bool aux
 
        if (aux_clock) {
                /* Auxiliary clocks are similar to TAI and do not have leap seconds */
-               if (txc->status & (STA_INS | STA_DEL))
+               if (txc->modes & ADJ_STATUS &&
+                   txc->status & (STA_INS | STA_DEL))
                        return -EINVAL;
 
                /* No TAI offset setting */
@@ -2661,7 +2662,8 @@ static int timekeeping_validate_timex(const struct __kernel_timex *txc, bool aux
                        return -EINVAL;
 
                /* No PPS support either */
-               if (txc->status & (STA_PPSFREQ | STA_PPSTIME))
+               if (txc->modes & ADJ_STATUS &&
+                   txc->status & (STA_PPSFREQ | STA_PPSTIME))
                        return -EINVAL;
        }