3.16.7-ckt8 -stable review patch. If anyone has any objections, please let me know.
------------------ From: John Stultz <[email protected]> commit 29183a70b0b828500816bd794b3fe192fce89f73 upstream. Additional validation of adjtimex freq values to avoid potential multiplication overflows were added in commit 5e5aeb4367b (time: adjtimex: Validate the ADJ_FREQUENCY values) Unfortunately the patch used LONG_MAX/MIN instead of LLONG_MAX/MIN, which was fine on 64-bit systems, but being much smaller on 32-bit systems caused false positives resulting in most direct frequency adjustments to fail w/ EINVAL. ntpd only does direct frequency adjustments at startup, so the issue was not as easily observed there, but other time sync applications like ptpd and chrony were more effected by the bug. See bugs: https://bugzilla.kernel.org/show_bug.cgi?id=92481 https://bugzilla.redhat.com/show_bug.cgi?id=1188074 This patch changes the checks to use LLONG_MAX for clarity, and additionally the checks are disabled on 32-bit systems since LLONG_MAX/PPM_SCALE is always larger then the 32-bit long freq value, so multiplication overflows aren't possible there. Reported-by: Josh Boyer <[email protected]> Reported-by: George Joseph <[email protected]> Tested-by: George Joseph <[email protected]> Signed-off-by: John Stultz <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Sasha Levin <[email protected]> Link: http://lkml.kernel.org/r/[email protected] [ Prettified the changelog and the comments a bit. ] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Luis Henriques <[email protected]> --- kernel/time/ntp.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index 3fca3fdd7c82..b1d6d26dbdc3 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -632,10 +632,14 @@ int ntp_validate_timex(struct timex *txc) if ((txc->modes & ADJ_SETOFFSET) && (!capable(CAP_SYS_TIME))) return -EPERM; - if (txc->modes & ADJ_FREQUENCY) { - if (LONG_MIN / PPM_SCALE > txc->freq) + /* + * Check for potential multiplication overflows that can + * only happen on 64-bit systems: + */ + if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) { + if (LLONG_MIN / PPM_SCALE > txc->freq) return -EINVAL; - if (LONG_MAX / PPM_SCALE < txc->freq) + if (LLONG_MAX / PPM_SCALE < txc->freq) return -EINVAL; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
