diff options
| author | John Stultz <[email protected]> | 2015-02-09 23:30:36 -0800 |
|---|---|---|
| committer | Ingo Molnar <[email protected]> | 2015-02-18 14:50:10 +0100 |
| commit | 29183a70b0b828500816bd794b3fe192fce89f73 (patch) | |
| tree | b0f40ccd43fb98fc1f9c03d65501442803a948fb | |
| parent | e07e0d4cb0c4bfe822ec8491cc06269096a38bea (diff) | |
ntp: Fixup adjtimex freq validation on 32-bit systems
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: <[email protected]> # v3.19+
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]>
| -rw-r--r-- | kernel/time/ntp.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index 4b585e0fdd22..0f60b08a4f07 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -633,10 +633,14 @@ 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; } |